For the past few weeks Ive been using the GymBoss Interval Timer, and its proven to be an excellent 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).