Lifehacker's favorite exercise tool RunKeeper has added a feature that's as creepy as it is useful. You can now opt to have your location and activity level broadcast live on your RunKeeper profile by using the iPhone app.

Initial creepiness aside, this is an opt-in feature and there are benefits to it. It's described as being "great for races, great for safety (so your spouse can track you)," and perfect for just plain showing off how far you're running.