Really simple

This DIY thermistor is based on NTC temperature sensor and relay PCB. It is programmable and can act as a heater or vice versa as a cooler.

It's cold so let's give power to the heating elements:

Oops. Now it's too hot so let's stop heating:

Temperature has fallen enough to exceed thresholds so let's start heating again:

Get smart

Get smart with S20 WiFi enabled socket. This really is a problem solver and last line of defense when everything else like computers fail. Simply switch off and on the whole system anywhere in the world with your phone app and hope for the best.

James Bond?

Not quite. This simple gadget is RF controlled 2-channel relay which comes handy in some cases.