It is very similar to an incubator I built a couple years ago with a cooler, heat tape, egg crate, water bottles and a thermostat. I had a thread hear explaining how to build it but since then the pictures have been removed...
http://www.ssnakess.com/forums/showthread.php?t=27896
It will work well and mine had a 100% hatch rate. The humidity is controlled by the egg chamber.