For the past few weeks Ive been using the GymBoss Interval Timer, and its proven to be an e****lent training companion. Fully programmable (and very simple) to train intervals where you want a specified time "on" and a specified time "off".

Tabata pushups/pullups/squats/situps... track work.. etc.
Gymboss Interval Timer: perfect for workouts : improves your body for life
It's ~$24 shipped to your door, and I received it within a few days. Very impressed with the product, especially since it was so affordable. There's a clip on the back in case you were wondering.. waistband works, or you can wear a watch and latch it onto the wrist band (been working out great for me on the track).