We (meaning I) have washed the key fob/opener for our van. It survived. We also washed and dried another one. It survived, but then when I tried to use it in the parking lot at the grocery store, the car suddenly (as we had used it several times before) didn't recognize the key and thought I was trying to break in and wouldn't stop honking.
That was fun.
Kids in the car, ice cream in the trunk, summertime, strangers giving me the hairy eyeball, and I am calling the dealership and the guy is laughing at me because he can hear the car honking in the background. I finally got it started and the honking stopped and drove right to the dealership to pick up my *new* key fob.
So for the automatic door opening key fobs, they can be washed. But don't dry them.
My favorite is when my son puts his wet pull-up in the wash and I don't discover it until I pull it out of the dryer. The lint trap will never be the same.