In have just gotten myself a new Cambridge (UK) phone number at SIPgate. I abandoned my land-line about a year and a half ago. A few months ago I started using Skype, but having an incoming geographic phone number could be useful.

I will have to try out Asterisk and see if I can set up a voicemail service. There are of course people who want to exploit free US local calls.

I had a similar idea but to do this for much for expensive mobile calls. The idea was that using a bluetooth enabled phone could find out if someone near by would let them place the call for free. I have a contract for my mobile phone service that gives me 1000mins/month for a flat fee. I of course do not use all of these. I would happily let other people use my free minutes. This would be a localised application. I would define what calls could be made and at what times.

Mobile operators would just hate it. The programming should not be too difficult as bluetooth is very much designed for transporting. Maybe if someone wants a task.