Here's a documented API for the Radio Thermostat company's line of Wifi thermostats (such as the Filtrete 3M50)
http://radiothermostat.com/documents/RTCOA%20WiFI%20API%20V1...
The RT line isn't as pretty as the Nest, but it's way cheaper.
http://radiothermostat.com/documents/RTCOA%20WiFI%20API%20V1...
The RT line isn't as pretty as the Nest, but it's way cheaper.
A quick look at programmable web turns up this... https://xively.com/