The Sunrize Izumo, one of the last two remaining japanese sleeper trainshas something like that - from necessity. The on board water supply is limitted, so a vending mashine on board sells a given ammount of shower-cards, that let you shower for an alotted number of minutes, counted with second precission on a LED display in the shower.

This way the on board shower will not run out of water & you get the opportunity to do a shower speedrun. :)