Waterpebble senses the water flowing around it, so no need to switch it on and off
It automatically times your first shower then uses that as a benchmark for future showers
A series of soft flashing lights indicate how much time you are spending compared to the benchmark, when it flashes red your time is up!
Over a number of showers the time taken to reach the flashing red slowly reduces to 2/3rds of the original time, encouraging you to save water, energy and money.