Fist bumps! Useful for expressing solidarity. IPhone bumps! Useful for trading massive amounts of sensitive financial information and personal data.

As Sarah Kessler reports over at Mashable, banking behemoth ING is now letting customers transfer funds from smartphone to smartphone, all with the simple tap of a handset. The app is free, and currently available for Apple iPhones running iOS 3.1.3 or higher.

The ING app is powered by something called Bump, a technology developed by a couple of business school students out in San Francisco. Bump uses sensors on the iPhone to transmit data between two phones, which sounds a little frightening, but according to the team at Bump, is actually totally safe. (Full Bump FAQ here.) Until the ING app hit the market, Bump tech was mostly a contact-sharing thing –– instead of thumbing in data, you just tapped.

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“We expected Bump to be used in formal situations, like replacing business cards, but when we looked at how people were actually using it, it was for fun, after five,” Bump co-founder Jake Mintz recently told USA Today. “It became a nights and weekends app, people using it in social situations. So once we saw that, we shifted to trying to emphasize fun over serious, like sharing music and photos.”

And money. Don't forget money.

All this bumping, it's worth pointing out, is a kind of precursor to near-field communication, or NFC –– a functionality that is expected to become increasing popular in coming years. Back in March, several outlets, including this one, reported that the iPhone 5 –– again, a phone that may or may not exist –– could come equipped with NFC technology.

"An entrepreneur who is working on a top-secret NFC product told me today that he believes the iPhone 5 will have NFC and cited a friend who works at Apple as a reliable source for the information," Elizabeth Woyke at Forbes wrote. "To further bolster his statement, the entrepreneur said that manufacturers of NFC readers – whom he has been talking to for his own product – also expect the iPhone 5 to have NFC."

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