I recently came across this project: A Mutual Friend:

A Mutual Friend attempts to explore how your mobile phone can act as a platform for cultural experiences; as a medium for reflecting on the human condition and as a means for making creative interventions in daily life.

The project sets out to propose and develop a mobile phone application which engages with the developing patterns of social behaviour in relation to mobile phones.

The project included the development of an interesting application:

prototype mobile phone application called ‘Hitchers’ that might form the basis of a range of future experiences. A hitcher is a small program that can be created by a user on their phone and released in a given cell in the network. Hitchers pass from phone to phone and cell to cell, moving across the country, interacting with people and collecting information as they go. The creator of a hitcher can view its progress using an online interface, seeing where it has been, who it encountered and what it found out, as might people who have given it a ride.

Here is the interface:

In Hitchers, the streets are full of people who are trying to hitchhike their way across the city or up and down the country. Hitchers are trying to find their way home, reach a specific destination, carry out a mission, or just share a journey with a stranger.