The paper reports on the Cellmusic system: a real-time, wireless distributed composition and performance system designed for domestic mobile devices. During a performance, each mobile device communicates with others, and may create sonic events in a passive (non interactive) mode or may influence the output of other devices. Cellmusic distinguishes itself from other mobile phone performance environments in that it is intended for performance in ad hoc locations, with services and performances automatically and dynamically adapting to the number of devices within a given proximity. It is designed to run on a number of mobile phone platforms to allow as wider distribution as possible, again distinguishing itself from other mobile performance systems which primarily run on a single device. Rather than performances being orchestrated or managed, it is intended that users will access it and create a performance in the same manner that they use mobile phones for interacting socially at different times throughout the day. However, this does not preclude the system being used in a more traditional performance environment. This accessibility and portability make it an ideal platform for sonic artists who choose to explore a variety of physical environments (such as parks and other public spaces).