How detect a leaky toilet and automatically stop it

[Matt Fitzgerald]

Hi All, 

I recently had my rental property's water bill spike and have had an accidental flood in the past year.  Both where due to toilets.  One toilet was running and the other overflowed. 

My question - Does anyone know of a solution, tool or part, that will stop the toilet if a leak is detected (assume that no one is home when these issues occur)?

Thanks,

Matt
Boston, MA