Runners greatly benefit from controlled fartlek workout referred as 30-20-10. run302010 is an excellent tool for the 30-20-10 workout and a great companion for any run tracking application used on a smartphone. Start run302010 on Pebble during your run. It counts the seconds for you, signals end of each interval by a short vibration, and displays actual time, so Pebble still serves as a watch.