I recently began a walk/run program to improve cardiovascular function. Although I weight train routinely I had allowed aerobic activities to decrease in the past couple of years. In pursuing this I found an iPhone app that is useful for me and perhaps for others. It is called 'Runmeter', or, in other incarnations 'Walkmeter' and 'Cyclemeter'. It has the same engine in each, and each can accommodate walking, running, and cycling. It uses GPS and maps. The GPS is extremely accurate--in a two mile stretch it may only vary by 0.01 mile--and this may be occasioned by my own path variation. The app has been reviewed highly, and I think it is neat. Furthermore, it's inexpensive.
http://www.abvio.com/runmeter/
