I've just released an iPhone app, called You Owe Me, which syncs purchases and repayments between people, using FB connect and/or normal email/password login. I

I've just released an iPhone app, called You Owe Me, which syncs purchases and repayments between people, using FB connect and/or normal email/password login. I think it's a pretty exciting space really, with a lot of potential. Signed up for their private beta - will see how it develops.