This is a bit off-topic but I'm wondering if I'm going to have to hack baresip to implement it:

Is there such thing as a SIP to mobile phone bridge, so that you can make phone calls over the net via a mobile phone that is in some remote location?

The application in my case is making local calls in a country that is expensive to call into. If it exists its the kind of thing that is resistant to search, unless it's called something I'm not aware of.

Edit: I think I might be looking for a SIP GSM Gateway running on an Android phone

To clarify I'm looking for:

initiate voip handset call => internet => call is initiated from remote mobile phone

remote mobile phone receives call => internet => voip handset rings

Or put another way something that exposes the Android phone as a trunk line.