Fitbit Zip is not just a water proof activity tracker. Yesterday, it is proved itself that it can also survive after 30 minutes warm-water washing and 50 minutes drying. I forgot to take it out from my jean pocket before I put it in laundry room.
This is the picture I took today. It is clean and smelled like fresh air.
The back of tracker has a cover with rubber O-ring. That is way it is water proof.