I don`t see much sense in making my wallet public. IMHO, this system would be useful only in form when Point of Sale generates temporary bitcoin account just like MTGox does now. But in such case bluetooth is not appropriate (in public places it's use may be misleading), QR code should be used instead.As far as I know, Bitcoin e-shop API already exists, so QR code generation and transaction processing (on Point of Sale side) is not to hard to implement. Also, mobile bitcoin java client exists (written bysomebode from Google), as far as free QR codes processing libraries. I think, we will see prototype implementation in few months. On the other hand, current market instability prevents further bitcoin adoption