I just finished a preliminary read-only (think version 0.1) wrapper around the Nest Thermostat API that is used by their mobile phone and web applications. As Nest doesn’t have a formal API yet, the code could break at any time and may not be suitable for any use. However, it is working today.
There are three projects, with the lib containing the assembly that is used by the two test applications. One is a console app and the other a simple WPF application:
(My thermostats are named Zero, One, and Two).
If there’s interest, I plan on adding some methods to the library which allow modification of data (such as the current temperature), and ideally, support for live updates from the devices if I can make sense of the data that is returned.
FYI: I’ve now written a Node version of the API, detailed here.