I just came across this interesting device:
It is a little timer board that can be configured to limit the amount of time a 12VDC device will run after power is applied. It would be very easy to use it to limit the amount of time that a rig's water pump can run in a single power cycle. This would be valuable protection against pumping the whole fresh water tank onto the floor of your rig in case of a plumbing failure in an unattended unit.
I know that many people power off their pumps when leaving the rig, but even if you do so, this mod would provide a valuable and extremely inexpensive backup.