I've seen that on The Caravan Channel and it looks great for site showers
I wouldn't use one in the caravan as all water has to be carried to the van and the waste has to be carried to the emptying point so long showers are not desirable unless you have a service pitch or a water carrier servant !
I like the trigger operated shower heads that give just the water you demand
Also a good reason for a pressure system as raised on another thread
You let go of the shower trigger and the pump shuts off due to the back pressure