I use the timer countdown function on the hills for hill reps. I don't like hill reps with a jog back recovery, much prefer a shorter recovery say 30 secs. I set the countdown to 1 - 2 mins and find a long climb. I can concentrate on the running, the bleep tells me the rep is up, I walk down hill (extends the amount of up I have) for 30 secs, then kick off up hill again until the bleep goes and repeat.