I recommend the http://www.rest-timer.com Great for making the workout more interesting and helps to reinvigorate you. Good stuff. and cheap too.

This company called Goodtech has develped this product called the Wristband Rest Interval timer. It is awesome. It is all preset and preprogrammed for the optimal rest period between sets. Only one press is required. Check it out... at http://www.rest-timer.com Good workout to everyone! Best regards...