The "knuckle bump" has clearly become a part of our culture as an informal means of salutation or as a high-five. It's no surprise that it's been incorporated in the "Bump" iPhone app, as a means for sharing contact information and photos. This is done wirelessly between 2 iPhone users.
You only need to gently bump fists with another iPhone user, while each person grasps his/her iPhone. This can serve as a high-tech way of swapping business cards, but instead paperlessly. I've been using this to share photos amongst my friends without having to email them. Check it out - it's a free app.
I'm closely watching to see if the company will expand on this and incorporate the sending of PDFs files. I envision bumping fists with a medical student at the end of the shift. "Nice job, dude. Now go read this article on NOT treating asymptomatic hypertension in the Emergency Department that I just bumped to you." How fun would that be?!
Video demonstrating Bump in action: