Bump is an API that allows developers to implement Bump services to their IOS or Android applications.
Bump is a service that allows to share data between two smartphones when they shake each other.
There are two parts to Bump: the app running on your device and a smart matching algorithm running on Bump servers in the cloud. The app on your phone uses the phone's sensors to literally "feel" the bump, and it sends that info up to the cloud. The matching algorithm listens to the bumps from phones around the world and pairs up phones that felt the same bump. Then Bump just route information between the two phones in each pair.
Bump service was bought by Google on late 2013 and planned to be closed on January 2014.