I have a homemade OWB and what I did was to purchase a couple of these.
http://www.ebay.com/itm/221623465322?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT This particular unit only has one 10 amp relay and operates on 12 volts.
My sensors, relays and draft solenoid operate on 12v dc. Powered by a 12 volt, 2 amp pc periphial power suppy. My solenoid sensor is inside the house attached to incoming water line, where I can monitor and also adjust, if desired. I find that I can keep an eye on the temperature and tell when wood is needed.
If you pull up ebay and use these search terms, "temperature controller relay", you'll find many different configurations. Some operate on 110 volts. Some are in celcius. Some have 2 or more relays, which is what you'd probably need to light up 3 different leds. Some of the controllers have built in piezo buzzer alarm, which might be good if you didn't actually want to monitor or was asleep.
I realize these things are made in china but I've tested them and they work fine for me, so far. Truth be told, my guess is most of the electronics we buy in america at inflated prices are probably made in china anyway.