I stumbled across this app in the iTunes store but dismissed it thinking it required the foot pod and specific Nike shoes, after closer inspection I discovered that it was a stand-alone application that only cost $2.49 with no other hardware required aside from your iPhone or iPod Touch. With the application running in my backpack and the headphones on I was able to listen to my own music and receive regular updates of my total distance and current speed. At the end of the run you get an accurate map of the course that has been plotted by GPS and your run is colour coded based on your speed throughout. (Green for your fastest for the day, red for the slowest and shades of yellow for everything in between.)
This application is amazing value and i would happily pay x10 the price. It is clear and simple, easy to use and very accurate*. I would sooner leave my shoes at home than run without this as it really pushes me to exceed my previous distance and times each and every time I run.
(*I have only used it on the lower north shore with an iPhone 4, different versions of the iPhone and different areas may effect the GPS reception)