Get a GymBoss interval timer. Great for exercise, and can accomplish this perception thing. (it has a vibrate-only mode). http://www.amazon.com/Gymboss-Interva

Get a GymBoss interval timer. Great for exercise, and can accomplish this perception thing. (it has a vibrate-only mode). http://www.amazon.com/Gymboss-Interval-Timer-Stopwatch-METALLIC/dp/B00CH05BLO/ http://www.amazon.com/Gymboss-Interval-Timer-Stopwatch-METAL...