And my award for innovative user interface for 2008 goes to the concept of Shake & Share, as illustrated by Zeptopad and Friendbook apps for the iPhone. Both solve the problem of sharing info (e.g. transferring a contact from one iPhone to another), by holding the iPhones together and shaking them.
I'm not sure how this works, but I can think of two possibilities: either the app uses a central server somewhere in the cloud, which acts as a broker for the sharing, or the devices initiate a bluetooth connection between each other. In either case, the accelerometer in the iPhone is used to generate a shared secret - if the iPhones are shaken together, they end up with the same shared secret.
Video below. Shakey Sharey bit towards the end.