That's such an awesome idea, I have no clue why it wasn't obvious to me before (That is to say, a mark of all brilliant ideas). This requires physical contact, very good on battery power, and actually creates an incentive for personal micro-transactions.

what is the incentive?

I'd say the novelty of it is enough of an incentive for such an idea. Also, bumping two phones together carries lower psychological cost than handing someone your hard-earned cash and I would expect people to have less qualms about lending/returning/trading small sums of money this way.

Yeah, while this seems to have some weird geeky appeal, it's still way harder than just pulling out a dollar and handing it to someone.

I've been in many scenarios (a lan party comes to mind) where there were multiple people who had either large bills or no cash at all, and yet we needed to buy things like beer or pizza.

This makes it very easy for people to transact small amounts of money (ideally free through paypal) using this technology. People may forget their cash, but they never forget their phone. Neat.

Brian

The API identifies the phone you bumped with, and then gives the app a channel to send messages between them. You can do pretty much anything with that. :)

Is there a fee for using the API?

The api will be free for most people. If you use it for revenue generating transactions or it is core to your app (wouldn't be useful without it) we ask for a revenue share (but no up front fee). Otherwise, as long as you don't hit our generous usage limits, it is free. The one exception is that contact sharing apps aren't allowed yet, although we have a plan to allow that in the next release.

Have thought about this a lot too