It has been done before in many variations here on the forum, but here is mine.
I did a search for "aquarium thermostat" on eBay and found a Chinese BuyItNow for something around $35 including shipping.
When received, I drilled a hole roughly the same width and depth as the thermostat's included sensor diode, then just pushed it in.
The thermostat is hooked up as an on/off controller, it does not supply the AC power itself. The Lyman heater is serial wired to the AC source for the thermostat.
When all was done, I simply set the thermostat for 32 degrees Celcius (90 Fahrenheit) and let it work its magic. When it reached 32.5 it clicked off and then clicked back on when the temp dropped to 31.5. The temperature is very even and my lubing with Carnauba Red works like a charm.