The wahoo Fitness Running set for the iPhone makes it possible to display heart rate and other training data on the iPhone. The small receiving plug receives data of sensors, i.e. of a chest strap, and transmits them directly to the iPhone. Apps of Fisica or NC-17 (available via iTunes in the App-Store) analyse the data. This is how iPad and iPhone get compelte training computers and you get music, telephone, pulse monitor, and fitness program in one set !