A 
system for monitoring and directing athletic or other physical activities is disclosed. In one embodiment of the invention, a 
headset worn by an athlete includes one or more sensors, a 
microprocessor, a non-
volatile memory and a 
communication link. The athlete's 
headset receives and transmits signals to a coach while the athlete is performing an activity. In this embodiment, the present invention provides coordinated audio streams to the athlete during his / her activity and training. In one implementation, the 
system coordinates audio for entertainment (such as music), audio expression of real-time performance information (such as count of laps, 
heart rate, etc.), optional pre-planned activity instructions and interrupt audio such as a coach's advice / instruction, or 
cell phone messages. In this implementation, the 
system records the output of the performance sensors for later analysis and allows for real-time display of the data for the coach. In one implementation, the system includes a 
underwater communication link for communication with a swimmer while in the water.