I only take off my watch when I shower. I even go swimming with my watch. Something like this is really slick, but I have trouble as it is remembering to charge my phone...
Obvious solution is to make a charger for the shower, similar to the ones electric toothbrushes use. Since it lasts 7 days, we can surely hope you take a shower within that time period =)
However, if it only needs to be recharged every 7 days, I could recharge it along w/ my fitbit each weekend.