diff --git a/packages/contracts/buidler.config.ts b/packages/contracts/buidler.config.ts
index 6dffc0757a136..c9449f34ae630 100644
--- a/packages/contracts/buidler.config.ts
+++ b/packages/contracts/buidler.config.ts
@@ -1,4 +1,5 @@
-import { usePlugin, BuidlerConfig } from '@nomiclabs/buidler/config'
+import * as path from 'path'
+import { usePlugin, BuidlerConfig, task } from '@nomiclabs/buidler/config'
 
 import {
   DEFAULT_ACCOUNTS_BUIDLER,
@@ -27,6 +28,18 @@ const parseSolppFlags = (): { [flag: string]: boolean } => {
   return flags
 }
 
+task('compile')
+  .addFlag('ovm', 'Compile using OVM solc compiler')
+  .setAction(async (taskArguments, bre: any, runSuper) => {
+    if (taskArguments.ovm) {
+      bre.config.solc = {
+        path: path.resolve(__dirname, '../../node_modules/@eth-optimism/solc'),
+      }
+      bre.config.paths.artifacts = './build/ovm_artifacts'
+    }
+    await runSuper(taskArguments)
+  })
+
 const config: BuidlerConfig = {
   networks: {
     buidlerevm: {
diff --git a/packages/contracts/contracts/optimistic-ethereum/bridge/L1CrossDomainMessenger.sol b/packages/contracts/contracts/optimistic-ethereum/bridge/L1CrossDomainMessenger.sol
index d168fa5750682..7460a103421c1 100644
--- a/packages/contracts/contracts/optimistic-ethereum/bridge/L1CrossDomainMessenger.sol
+++ b/packages/contracts/contracts/optimistic-ethereum/bridge/L1CrossDomainMessenger.sol
@@ -19,6 +19,8 @@ contract L1CrossDomainMessenger is BaseCrossDomainMessenger, ContractResolver {
 
     event RelayedL2ToL1Message(bytes32 msgHash);
 
+    address public l1ToL2QueueAddress;
+
     /*
      * Data Structures
      */
@@ -44,6 +46,11 @@ contract L1CrossDomainMessenger is BaseCrossDomainMessenger, ContractResolver {
         ContractResolver(_addressResolver)
     {}
 
+    function tempInit(address _l1ToL2QueueAddress) public {
+        require(l1ToL2QueueAddress == address(0));
+        l1ToL2QueueAddress = _l1ToL2QueueAddress;
+    }
+
 
     /*
      * Public Functions
@@ -236,7 +243,10 @@ contract L1CrossDomainMessenger is BaseCrossDomainMessenger, ContractResolver {
         view
         returns (L1ToL2TransactionQueue)
     {
-        return L1ToL2TransactionQueue(resolveContract("L1ToL2TransactionQueue"));
+        if (l1ToL2QueueAddress == address(0)) {
+            return L1ToL2TransactionQueue(resolveContract("L1ToL2TransactionQueue"));
+        }
+        return L1ToL2TransactionQueue(l1ToL2QueueAddress);
     }
 
     function resolveStateCommitmentChain()
diff --git a/packages/contracts/contracts/optimistic-ethereum/bridge/L2CrossDomainMessenger.sol b/packages/contracts/contracts/optimistic-ethereum/bridge/L2CrossDomainMessenger.sol
index 1dc0e69358a60..4d8742f8a1bec 100644
--- a/packages/contracts/contracts/optimistic-ethereum/bridge/L2CrossDomainMessenger.sol
+++ b/packages/contracts/contracts/optimistic-ethereum/bridge/L2CrossDomainMessenger.sol
@@ -21,6 +21,8 @@ contract L2CrossDomainMessenger is BaseCrossDomainMessenger {
     address private l1MessageSenderPrecompileAddress;
     address private l2ToL1MessagePasserPrecompileAddress;
 
+    address public authenticatedAddress;
+
     /*
      * Constructor
      */
@@ -102,9 +104,17 @@ contract L2CrossDomainMessenger is BaseCrossDomainMessenger {
             bool
         )
     {
-        IL1MessageSender l1MessageSenderPrecompile = IL1MessageSender(l1MessageSenderPrecompileAddress);
-        address l1MessageSenderAddress = l1MessageSenderPrecompile.getL1MessageSender();
-        return l1MessageSenderAddress == targetMessengerAddress;
+        if (authenticatedAddress == address(0)) {
+            IL1MessageSender l1MessageSenderPrecompile = IL1MessageSender(l1MessageSenderPrecompileAddress);
+            address l1MessageSenderAddress = l1MessageSenderPrecompile.getL1MessageSender();
+            return l1MessageSenderAddress == targetMessengerAddress;
+        }
+        return msg.sender == authenticatedAddress;
+    }
+
+    function tempInit(address _authenticatedAddress) public {
+        require(authenticatedAddress == address(0));
+        authenticatedAddress = _authenticatedAddress;
     }
 
     /**
diff --git a/packages/contracts/contracts/optimistic-ethereum/queue/L1ToL2TransactionQueue.sol b/packages/contracts/contracts/optimistic-ethereum/queue/L1ToL2TransactionQueue.sol
index e6251870b7191..e8537aa944b54 100644
--- a/packages/contracts/contracts/optimistic-ethereum/queue/L1ToL2TransactionQueue.sol
+++ b/packages/contracts/contracts/optimistic-ethereum/queue/L1ToL2TransactionQueue.sol
@@ -30,6 +30,8 @@ contract L1ToL2TransactionQueue is ContractResolver, RollupQueue {
 
     uint constant public L2_GAS_DISCOUNT_DIVISOR = 10;
 
+    address public l1MessengerAddress;
+
     /*
      * Constructor
      */
@@ -49,6 +51,11 @@ contract L1ToL2TransactionQueue is ContractResolver, RollupQueue {
      * Public Functions
      */
 
+    function tempInit(address _l1MessengerAddress) public {
+        require(l1MessengerAddress == address(0));
+        l1MessengerAddress = _l1MessengerAddress;
+    }
+
     /**
      * Checks that that a dequeue is authenticated, and dequques if authenticated.
      */
@@ -69,6 +76,8 @@ contract L1ToL2TransactionQueue is ContractResolver, RollupQueue {
     )
         external
     {
+        require(l1MessengerAddress == address(0) || msg.sender == l1MessengerAddress);
+
         uint gasToBurn = _ovmGasLimit / L2_GAS_DISCOUNT_DIVISOR;
         resolveGasConsumer().consumeGasInternalCall(gasToBurn);
 
diff --git a/packages/contracts/package.json b/packages/contracts/package.json
index 030ce063a5ca6..7912295506fd2 100644
--- a/packages/contracts/package.json
+++ b/packages/contracts/package.json
@@ -1,12 +1,13 @@
 {
   "name": "@eth-optimism/rollup-contracts",
   "private": true,
-  "version": "0.0.1-alpha.33",
+  "version": "0.0.1-alpha.35",
   "main": "build/index.js",
   "files": [
     "build/**/*.js",
     "build/contracts/*",
-    "build/artifacts/*json"
+    "build/artifacts/*json",
+    "build/ovm_artifacts/*json"
   ],
   "license": "MIT",
   "workspaces": {
@@ -29,6 +30,7 @@
     "coverage:contracts": "cross-env SOLPP_FLAGS=\"FLAG_IS_TEST\" buidler coverage --network coverage --show-stack-traces --testfiles \"test/contracts/**/*.spec.ts\"",
     "build": "yarn run build:contracts && yarn run build:typescript && yarn run build:copy",
     "build:contracts": "buidler compile",
+    "build:contracts:ovm": "buidler compile --ovm",
     "build:typescript": "tsc -p .",
     "build:copy": "yarn run build:copy:contracts",
     "build:copy:contracts": "copyfiles -u 2 \"contracts/optimistic-ethereum/**/*.sol\" \"build/contracts\"",
@@ -37,7 +39,8 @@
     "lint:typescript": "tslint --format stylish --project .",
     "fix": "yarn run fix:typescript",
     "fix:typescript": "prettier --config ../../prettier-config.json --write \"index.ts\" \"buidler.config.ts\" \"{src,test,plugins}/**/*.ts\"",
-    "deploy:all": "env DEBUG=\"info:*,error:*,debug:*\" node ./build/src/exec/deploy-contracts.js"
+    "deploy:all": "env DEBUG=\"info:*,error:*,debug:*\" node ./build/src/exec/deploy-contracts.js",
+    "prepublish": "yarn run build && yarn run build:contracts:ovm"
   },
   "dependencies": {
     "@ethersproject/keccak256": "5.0.3",
diff --git a/packages/ovm-toolchain/README.md b/packages/ovm-toolchain/README.md
index 87a80dbb7a6a7..8cc701eeec3f1 100644
--- a/packages/ovm-toolchain/README.md
+++ b/packages/ovm-toolchain/README.md
@@ -86,4 +86,30 @@ const config = {
 }
 
 export default config
+```
+
+#### Watcher
+Our `Watcher` allows you to retrieve all transaction hashes related to cross domain messages such as deposits and withdrawals. In order to use, first send a transaction which sends a cross domain message, for example a deposit from L1 into L2. After sending the deposit transaction and storing the transaction hash, use `getMessageHashesFromL1Tx(l1TxHash)` to get an array of the message hashes of all of the L1->L2 messages that were sent inside of that L1 tx (This will usually just be a single element array, but it can return multiple if one L1 transaction triggers multiple deposits). `getMessageHashesFromL2Tx(l2TxHash)` does the same for L2->L1 messages. `onceL2Relay(messageHash, callback)` takes in an L1->L2 message hash and a callback that will be triggered after 2-5 minutes with the hash of the L2 tx that the message ends up getting relayed in. `onceL1Relay(messageHash, callback)` does the same for L2->L1 messages, except the delay is 7 days.
+
+```typescript
+import { Watcher } from '@eth-optimism/ovm-toolchain/'
+import { JsonRpcProvider } from 'ethers/providers'
+
+const watcher = new Watcher({
+  l1: {
+    provider: new JsonRpcProvider('INFURA_L1_URL'),
+    messengerAddress: '0x...'
+  },
+  l2: {
+    provider: new JsonRpcProvider('OPTIMISM_L2_URL'),
+    messengerAddress: '0x...'
+  }
+})
+const l1TxHash = (await depositContract.deposit(100)).hash
+const [messageHash] = await watcher.getMessageHashesFromL1Tx(l1TxHash)
+console.log('L1->L2 message hash:', messageHash)
+watcher.onceL2Relay(messageHash, (l2txhash) => {
+  // Takes 2-5 minutes
+  console.log('Got L2 Tx Hash:', l2txhash)
+})
 ```
\ No newline at end of file
diff --git a/packages/ovm-toolchain/package.json b/packages/ovm-toolchain/package.json
index 40e9ef6520866..6a838a0982518 100644
--- a/packages/ovm-toolchain/package.json
+++ b/packages/ovm-toolchain/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@eth-optimism/ovm-toolchain",
-  "version": "0.0.1-alpha.7",
+  "version": "0.0.1-alpha.8",
   "description": "Wrappers for Ethereum dev tools",
   "private": true,
   "main": "build/index.js",
diff --git a/packages/ovm-toolchain/src/index.ts b/packages/ovm-toolchain/src/index.ts
index c459e1ce7c202..06c06a454cafa 100644
--- a/packages/ovm-toolchain/src/index.ts
+++ b/packages/ovm-toolchain/src/index.ts
@@ -1,3 +1,4 @@
 export * from './ganache'
 export * from './waffle'
 export * from './x-domain-utils'
+export * from './watcher'
diff --git a/packages/ovm-toolchain/src/watcher.ts b/packages/ovm-toolchain/src/watcher.ts
new file mode 100644
index 0000000000000..8bbdec8a845af
--- /dev/null
+++ b/packages/ovm-toolchain/src/watcher.ts
@@ -0,0 +1,68 @@
+/* External Imports */
+import { ethers } from 'ethers-v4'
+
+interface Layer {
+  provider: any
+  messengerAddress: string
+}
+
+interface WatcherOptions {
+  l1: Layer
+  l2: Layer
+}
+
+export class Watcher {
+  public l1: Layer
+  public l2: Layer
+
+  constructor(opts: WatcherOptions) {
+    this.l1 = opts.l1
+    this.l2 = opts.l2
+  }
+
+  public async getMessageHashesFromL1Tx(l1TxHash: string): Promise<string[]> {
+    return this._getMessageHashesFromTx(true, l1TxHash)
+  }
+  public async getMessageHashesFromL2Tx(l2TxHash: string): Promise<string[]> {
+    return this._getMessageHashesFromTx(false, l2TxHash)
+  }
+
+  public onceL2Relay(msgHash: string, callback: Function): void {
+    return this._onceRelay(false, msgHash, callback)
+  }
+
+  public onceL1Relay(msgHash: string, callback: Function): void {
+    return this._onceRelay(true, msgHash, callback)
+  }
+
+  private async _getMessageHashesFromTx(
+    isL1: boolean,
+    txHash: string
+  ): Promise<string[]> {
+    const layer = isL1 ? this.l1 : this.l2
+    const l1Receipt = await layer.provider.getTransactionReceipt(txHash)
+    const filtered = l1Receipt.logs.filter((log: any) => {
+      return (
+        log.address === layer.messengerAddress &&
+        log.topics[0] === ethers.utils.id('SentMessage(bytes32)')
+      )
+    })
+    return filtered.map((log: any) => log.data)
+  }
+
+  private _onceRelay(isL1: boolean, msgHash: string, callback: Function) {
+    const layer = isL1 ? this.l1 : this.l2
+    const filter = {
+      address: layer.messengerAddress,
+      topics: [
+        ethers.utils.id(`Relayed${isL1 ? 'L2ToL1' : 'L1ToL2'}Message(bytes32)`),
+      ],
+    }
+
+    layer.provider.on(filter, (log: any) => {
+      if (log.data === msgHash) {
+        callback(log.transactionHash)
+      }
+    })
+  }
+}
diff --git a/yarn.lock b/yarn.lock
index 673cb53a52ea1..807577a30d4ab 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -5410,32 +5410,6 @@ ethereumjs-common@^1.1.0, ethereumjs-common@^1.3.2, ethereumjs-common@^1.5.0:
     util.promisify "^1.0.0"
     uuid "^8.3.0"
 
-"ethereumjs-ovm@git+https://github.com/ethereum-optimism/ethereumjs-vm.git":
-  version "4.2.0"
-  uid "02ba6e77a88339b04a053b5e653f644acb1555b8"
-  resolved "git+https://github.com/ethereum-optimism/ethereumjs-vm.git#02ba6e77a88339b04a053b5e653f644acb1555b8"
-  dependencies:
-    "@types/debug" "^4.1.5"
-    "@types/uuid" "^8.3.0"
-    async "^2.1.2"
-    async-eventemitter "^0.2.2"
-    core-js-pure "^3.0.1"
-    debug "^4.1.1"
-    ethereumjs-account "^3.0.0"
-    ethereumjs-block "^2.2.2"
-    ethereumjs-blockchain "^4.0.3"
-    ethereumjs-common "^1.5.0"
-    ethereumjs-tx "^2.1.2"
-    ethereumjs-util "^6.2.0"
-    ethers "^5.0.0"
-    fake-merkle-patricia-tree "^1.0.1"
-    functional-red-black-tree "^1.0.1"
-    merkle-patricia-tree "^2.3.2"
-    rustbn.js "~0.2.0"
-    safe-buffer "^5.1.1"
-    util.promisify "^1.0.0"
-    uuid "^8.3.0"
-
 ethereumjs-tx@1.3.7, ethereumjs-tx@^1.1.1, ethereumjs-tx@^1.2.0, ethereumjs-tx@^1.2.2, ethereumjs-tx@^1.3.3:
   version "1.3.7"
   resolved "https://registry.yarnpkg.com/ethereumjs-tx/-/ethereumjs-tx-1.3.7.tgz#88323a2d875b10549b8347e09f4862b546f3d89a"