Ever had an aquarium leak?
Does your spouse get angry?
Does your neighbor like water pouring into their apartment?
Floors are expensive to replace.
Not to mention mold issues.
Here's a $10 insurance policy.

http://www.tbaquatics.com/shop/water-alarm-495.html
http://www.tbaquatics.com/shop/water-alarm-495.html
Clip the sensor to a ro di bucket or resevoir. Put one in your aquarium stand.
Can also be used for water heats, sumps, etc.