I've been using the ReefFanatic model (with 2 float sensors) for about 6 months now and its been running along fairly well. I did the one setup with one sensor in in my sump (sensor face up) so the controller knows when to add water, and one with the sensor face down in the refill tank to know if the water level is too low to pump any more. The setup has worked pretty good so far. If I remember correctly I think I payed around $85 for it.

Brian