Not as cute as a leakfrog, but cheaper than the ones currently shown on Deals.Woot!. And more available.
Loud (95dB) alarm sounds with direct water contact
Fully automatic operation, no wiring required
Floats and signals for up to 72-hours
Low battery warning for optimum performance
Includes three leak alert units, two 9-Volt batteries and detailed instructions
From the Manufacturer
Zircon's leak alert electronic water detector is now available in a three pack which also includes three 9-volt batteries for immediate use. Zircon's leak alert is perfect for use near water heaters, sinks, dishwashers, sump pumps, and more. Protect your home from water damage by placing leak alert anywhere the potential for flooding or leaks exist.
Note that the listing says two batteries in one place, and three in the other. I suspect three is correct.