Pffftttt! The DIADs are designed to take an ass-kicking. I once had mine fly out of the truck when I hit a bump and watched it bounce along the road whilst I was doing 50 km/h. I have also dropped mine in a puddle and had it completely submerged . . . still works fine, though the batteries are terrible when it's -30 out.
By the way, I carry mine.
Hmmm...the DIAD isn't waterproof. I realize it may have dropped in a puddle and been fine that time, but it's not waterproof. Seriously.