I believe the frequencies used for Caller ID are per Bell 202, a straight FSK data standard.

This is correct. Before Caller ID came along, about the only group backward enough to still be using Bell 202 are the amateur packet radio folks. So if you happen to be a ham with a packet TNC and a lot of spare time, you could consider reprogramming one to decode caller ID. Of course, you still have to sign up for the service before the CO will send you the data. And if your time is worth anything to you, it'd be better to just buy one of the modems that already has caller-ID built in. Phil