Those are pretty neat, but their advertised battery life is only 2 months (so I'm sure it's less than that). For the extra 50 bucks those Spot Protect sensors say they'll run for years before batteries need to be change, I like that peace of mind.
I can also vouch for using Waterbug Units with the Elk M1, simple, effective and you'll never out grow the M1 panels potential.
HOWEVER, I've stumbled across these WiFi water sensors (I run a small property management company) and these things are incredible...