An electronic switch? Water Witch seems to be the best one.
I found this thread on another forum regarding bilge pumps:
http://www.sailnet.com/forums/gear-m...-switch-2.html
the first post at the top of the page has what seems like good advice. He recommends using an electronic switch and running it to an automotive relay to prevent a short circuit.
Another article I read suggested using a smaller pump as the primary, and then mounting a larger pump higher, to handle emergencies. I was thinking about also wiring in a buzzer to this larger pump.