The Tickstill application is a fantastic stopwatch for our Nokia N900 with countdown, among other features.
Tickstill has an interface really nice and easy to use, as you can watch in this video.
[youtube]http://www.youtube.com/watch?v=6wtbESytVVg[/youtube]
Download | Tickstill
I’ve tried this application. It looks and works very nice, but I have one remark. Its default alarm sound is pretty ugly. But, of course that can be easily changed.