Bilgemate from Nautilus Marine monitors your bilge for water completely independently from your bilge pump system, and if it detects water it will immediately call or text you using the GSM global cellular network to advise you of the problem. 
12 or 24v DC operation and is available as a 2 or 4 zone monitoring system.

Peace of mind when your boat is in the water unattended
if water in the bilge is detected
Bilgemate immediately calls or sends text message to your phone 
allowing you to arrange service before any expensive damage occurs

Click on product data sheet link under price (above) for leaflet pdf