I have successfully built one of these dual stage controllers from a Vellemann kit. I am extremely impressed by this product and can't say enough good things about it. It has a large LED display. the Canadian and U.S. models display in fahrenheit. The settings for the high and and low setpoints are can be 0.1 F. The hystersis is also adjusted from from 0.1 Ff and up. The unit itself can also be calibrated against a accurate source. You do need to supply a transformer and a case. The instructions are a bit vague, but anyone with good soldering techniques and a some electronic basics can put it together easily.
http://www.qkits.com/serv/qkits/vell...ages/K6002.asp