HTML 5 run tracking application

An idea that I have had for awhile is a RunKeeper like application that runs completely in the browser. This is not due to any inherit issues with the RunKeeper application, just more of a proof-of-concept. HTML 5 makes this easy. We can save old runs and run without an Internet connection making it almost a native app.
The only phone I have tested this with is an iPhone 4S as that is the only phone I have access to.

