What's a good sports tracker app for iPhone?

I'm looking for an app for tracking activities like **walking, running or bicycling**. Lots of people I know with Android or Nokia phones use such apps, but I don't know what's a good option for iOS. Requirements: - Can track **time** & **distance** covered (using GPS) - Should be very simple to use: 1) start the tracker 2) go for the walk/run/ride 3) stop the tracker and see the distance & time - Available on App Store (i.e. works on non-jailbroken devices) **Preferably free**, but feel free to recommend an excellent paid app too if you know of one. Also, it's a plus if I can use the app for my simple needs **without signing up** to any service.