With the style workout I do predominately, the need for an interval timer is crucial... fortunately when I started doing tabata workouts I found the Gymboss timer and it's become probably my most used workout item. The company is in the states but does cheap shipping worldwide which is always a big help!
The Gymboss has a stopwatch function for when my aim is to beat my personal best time and it has an interval timer where I can set two different time intervals (as I would in a tabata workout of say 50sec and 10 sec) and can repeat this up to 99 times (a feat I've never attempted!). It has a beep and/or vibrate alarm which has a duration of 1,5 or 10 seconds.
It clips on to your belt, or for me I clip it to the collar of my top so I can see how long til I get to stop! And helpfully it is water and shock resistant so your sweat won't bust it!
This really is a good way to start your home workouts... cheaper than a week at the gym!