If you are concerned about running out of water whilst having a shower then this “shower head” will help. It has a built in trigger to control water flow thus saving water.
In fact this is a hand held bidet sprayer, also known as a shataff in the Middle East, it is a simple but effective cleaning product. It is used all over the world for simplicity in cleaning.
I bought it on ebay for £6.95 delivered and a simple swop with the existing shower head.