There are actually several automatic water main emergency shutoff valve products currently available. Some are expensive and some not so much. Typically they have a sensor that measures water flow changes at your house. When something abnormal occurs the water main valve is closed. The objective is to prevent water damage. Insurance companies will often give a good discount if you have one.
Also, several of the DYI home alarm systems have have wireless water sensor devices you can place in various places. When water is detected an alert will be sent.