I used to have a walkman that had a built in timer. You could set it for a certain interval (1 minute, 5 minutes, 3 minutes and 22 seconds, whatever) and it would beep, in the headphones, at that interval. So if you wanted to run for 5 minutes and walk for 5 minutes you could set the timer and it would let you know when 5 minutes were up.
Anyone have one of these? Know where I can get one new?