I EXPECT them to be ruined if I drop them onto a hard surface.
A shot timer is something held by a buddy above his head (often with sweaty, oily hands) while he runs behind you while you shoot targets on a gun range. It will be subjected to blowing sand, freezing temperatures, hot sun, smoke, dirty/oily fingers, and pouring rain. EXPECT them to be dropped on a hard surface eventually.
They aren't used the same way that electronic gadgets like iPods and lap tops are used. So the #1 factor in selecting a shot timer (apart from the fact it should of course work) is durability and thus reliability.