Actually, the zoo-med rheostat is completely analog, so you can dial it up and down to any point on the dial, not just three settings. As someone pointed out already, it does not have an exact temperature control so you have to “dial in” the temp you want through trial and error. An infrared thermometer is really helpful for this.
http://www.amazon.com/PE1-INFRARED-THER ... B0009O1G5K
I use the zoo-med temp controls on my under-tank heating pads. This allows me to put some warmth on their sleeping area, but prevent the area from becoming too hot.
The zilla thermostat is a pretty neat idea and the price is nice and reasonable. The other devices I’ve seen have run near $100 (USD), so this is much more approachable. If it cycles the heat on and off then it would also help keep the energy costs down, as those ceramic heaters use gobs of power.