Here's a really basic gadget that could help you save a whole lot of water. The Water Saver attaches to the end of a hose and displays how much water is being used in real time.
The digital display shows in gallons or liters how much water has been used, and gives you information you need to know when to shut off the hose. It's a great idea for outdoor water use, for example, figuring out how much water your plants really need, and watching to make sure you don't go over that amount.
It doesn't have an automatic shut-off for when you get to a certain amount, so it's up to you to set a limit and turn off the hose.
I don't know about the $25 price tag. It seems a bit expensive for a simple gauge and it'd probably take a few months of actively watching your water use to realize the return on investment. But even with the slightly high price, it seems like a really helpful gadget for being aware of how much water you're using in real time and not overdoing it.
What I'd love even more is if this were attached to an app so that you could save your data from the device, and see your outdoor water use habits over time. If something like that exists already, let us know in the comments!