Google recently acquired and shutdown the "bu.mp" product which had allowed developers to build mobile apps where users simply bump phones to exchange files, contact data (or add to social network), and in some cases p2p payments. Closer.io™ is a developer friendly platform that provides a more accurate version of the bu.mp technology as well as highly scalable backend and iOS/Android SDKs. It will also tie into a wide ecosystem of 3rd party APIs.
People are justly upset about Google shutting down bu.mp:
tweeted on 1/1/14, 10:36 AM
Google is killing Bump, and with it, the dream of dead-simple, cross-platform file transfers. ti.me/19IpIvF
Being the pathological hacker that I am, I've found a way to out-do the accuracy of bu.mp's technology on the phone itself and I have the experience to build a more scalable backend.
iOS/Android demo available. Requires ~4 months of further development for commercial grade API & SDK.