IOS – 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.