I also have one on my water bin, it's just one I bought at Wal-Mart. When I got it and compared it to a couple hang-in thermometers, it registers 2 degrees higher. So with that one, I know if I want 76 degree water, it has to read 78. So, then I bought the above Coralife one.
Just noticed the one I have doesn't have the alarm like the one you pointed to. Nice feature.
I have a small Lifeguard unit which I use routinely/chronically. It is always in some tank or another. Quite a good check against the error of stck-ons That I use on the tanks.
I really like the digital readout. The main advantage is being able to see small variations in temperature. You can see exactly how stable the tank temperature is.