Low cost ($100) WiFi thermostat also has Zigbee support?!?! This smells like it might be a hackable device. Might even be a PID controller? If it is you could partner something like this with Tweet a Watts, a chumby and you have a good start on DIY home automation. “there is space for a ZigBee module to be plugged into the back of the thermostat, as well as space for a module to enable demand response” I would like to see if I can get an FCC id off one and look at some board images.
Biohacking — Two Blood Meters to Start Your Biohacking Adventure
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Have you considered making a home thermostat kit? I’ve wanted a more open thermostat. None of the ones I’ve run into, even at $500, are all that flexible. If most of the programming happens over a web interface, the kit wouldn’t have to have very much of a UI.
From the documentation (PDF at homedepot.com) if the batteries run out, it will fail in whatever heating/cooling/off mode it was in, which seems poor – I’d always assumed you’d want a traditional mechanical thermostat fallback in the design, but I guess at $100 that’s a shortcut to be taken :-}
(All I want is to be able to have my logout script, when I leave work, set the heat back up before I get home. These days the "computer" part is easy (some little arduino and a zigbee or wifi-serial frob) but actually doing the control sanely is Real Work…)