Everything BrewPi does is a good start considering that is your main competition in the DIY fermentation controller space.
Considering this is a DIY, the OpenTroller board should be very cheap, otherwise you can build the same thing with $50 in equivilent parts for a BrewPi which would be a RaspPi and Arduino, but having both of those also gives you way more functionality and data logging capabilities than what im thinking your doing with the FermTroller.
With their latest software you can build something basically identical to this setup, except the OpenTroller board uses the Arduino/Pi setup. Its how i did it, I didnt bother buying their Arduino shield because i dont care about LCD screens or knobs or buzzers, and just hooked up the sensors and powerswitch tail II myself to the appropriate Arduino pins.
The web interface is where its at, not only can i see what my fermentation fridge is at anywhere in the world on my phone, i can set it.