These systems don't use Caller ID, I believe they use http://en.wikipedia.org/wiki/Automatic_number_identification http://en.wikipedia.org/wiki/Automatic_number

These systems don't use Caller ID, I believe they use http://en.wikipedia.org/wiki/Automatic_number_identification http://en.wikipedia.org/wiki/Automatic_number_identification which is more difficult (but not impossible) to spoof. I had pretty good luck with http://www.trapcall.com/ http://www.trapcall.com/ when I had a phone stolen and the thief called me back. Didn't get the phone back, but the system worked as promised.