I had one and it was Nike something. I don't know exactly what it was called and my phone broke so I can't look. It was really good and I used it all the time, it shows where you have gone and how far it was. It also times how long the run is.
If you have a certain Nike shoe then you can buy a Nike + chip at your local shoe store for around 20 dollars then if you have an iPhone you can turn on the Nike + iPod app and then it tracks how long you run/walk.