Well, to get back to your original question:

Will it work if you have service? Certainly.

Will it work if you don't have service? Don't know. Plug in a phone, if you get a dial-tone, it will work. What 308holes said about having a "default" service sounds like a really good idea, but I don't think it's universal.

In any event, I agree with what's already been said. It's kinda' gimmicky, doesn't seem to be that particularly useful, and has the potential to cause problems with existing phones. I really hope these devices don't proliferate. The phone system wasn't designed as an alternative power grid. I can see SBC/ATT mailing out letter bombs to people they find doing this sort of thing. <img src="/images/graemlins/smile.gif" alt="" />