Smart ASOV

Smart ASOV is a unique electronic float valve kit for all
  kinds of reservoir. Never worry about forgetting to turn off your RO/DI
  system or overfilling your reservoir again with this clever gadget! Simply
  mount the magnetically-mounted sensor to any reservoir/bucket/jug and the
  water will stop once the reservoir is filled. No tool is required and there
  is no unreliable float valve to fail. Smart ASOV provides you an easy, safe
  and efficient choice other than float valves.