I've just seen the ad for IKEA Skål!. If you haven't seen it, you can see the video linked. Basically, you can choose a drink and make a toast-like gesture (using the iPhone) with another person having the app. This results in both phones automatically exchanging names and photos, and optionally both of them will share the picture of their toast on Facebook. The ad is really nice, but I am curious about how it works.
[Edit]: As a commenter pointed out, there is also another application Bump, which use the same technique to perform similar (and even more) functionalities. The FAQ stated that this application was designed with personal and data security in mind, and uses various sensors and algorithms to "feel" the bump and the server will find matching bumps according to the sensor reading and algorithms.
How exactly does the iPhone know that I am toasting/bumping with another person? I mean I don't think GPS can track the phones that accurately. And how does it transfer the contacts and photos? And how can it correctly determine who is toasting with whom if there are multiple users in the same room? How is the security and confidentiality protected?