The demon dialer was a blue-box, sold by hacktic.
I wrote these tools to be able to dialing lots of phonenumbers relatively quickly, while recording information about whatever answered. I used to do this in order to find some way of accessing the early internet.
The idea was that the DEMON.COM program was sitting 'in the background', as a TSR. and monitoring certain keypresses, while i was editting a textfile with phonenumbers using 'qedit'.
When i pressed the right key, the DEMON TSR would pick up the phone, and control the demon-dialer to make the call.