>I've seen a California-designed house alarm with a built-in
>modem/communicator. On closer inspection (opening the damn thing) it
>turned out to be a 16MHz 16C74 doing to whole lot. Quite impressive.

But did it emulate an actual modem or just a DTMF-sender? An alarm just needs to send the touch-tone frequencies as far as I can understand, plus perhaps a digit or two to inform about the alarm type. Unless it's going to broadcast live via an onboard  camera and microphone.

The day someone writes PIC code to emulate a 300 bps or even an 1200 bps bidirectonal modem, and distribute the code public domain, THEN I will be impressed. ;-)