I haven't done this but I'm paranoid about doing it so this thread makes me happy. xD
I have dropped my Pokéwalker in the rain before. I was seeing a movie with a friend and it was pouring torrentially. We ran across the parking lot to a coffee shop and there I realized I didn't have my walker. D: So I ran back outside and found it halfway to the theatre just lying on the ground in the rain. It worked fine and has worked fine ever since so these things were built to last. xD
Mine broke when it got dropped on a carpeted floor imediatly after buying it new. 0_0 My friend gave me another one, but I'm extremly paranoid about dropping it.
My Pokewalker never went through the wash. But, I do have another story...
I lost my Pokewalker at my grandparents when I was sitting in a recliner chair. After about a month, I found it. That very day, it fell out of my pocket again, and my grandma's dog chewed the crap out of it. Unfortunately, it doesn't work anymore. D: