I think mid xx at present. Maybe low to mid xxx at best if the growth happens.
I'm gadgety and I don't see the growth in this area happening - bluetoothing was pretty big a few years ago (you'd receive a picture, of yourself, whilst sat in a pub - that kind of thing.)
Check out http://www.helio.com and check out the buddy beacon feature on their network and handsets. I think that this will develop and become bigger.
The tech stuff:
They are in US, using sprints network (cdma and 3g) have unlimited data and the device can show your position (gps) plus the buddy beacon feature shows your friends' position on the map (if they have switched this feature on)
Messaging between wouldn't be bluetooth (because of short range) but would be over the network.