iRunner™ App
I am currently using this app with the Digifit Connect and my heart rate monitor and foot pod to track my runs. Tracking heart rate is great and really useful. The previous version of the app wasn't super-stable on the iPhone 4 but they seem to have resolved most of the issues in this version. This is the first version with GPS and the first couple of times I used it I got endless messages about GPS accuracy not being high enough, but now that it is set to use GPS even if it is only accurate to 100 meters, it is fine (and of course it then accurately maps my runs to say a meter).