If you're looking for ways to use less water, Instructables user tamberg developed a DIY water sensor that shows you when you've gone through a litre.
Photo by tamberg
Using an Arduino, flow sensor and coloured LEDs, tamberg set up the device to change colours from blue to red when a litre has been consumed. For simple tasks, like washing your hands, that's plenty of water to get the job done. It's often easier to use less of something just by knowing how much you're really using, and this can help maintain your awareness.
Some soldering is required, but if you're interested in building your own, check out the link below. To see it in action, check out the video here.
Augmented Water [Instructables]