Nest Thermostat. It is very cool smart thermostat made by Google. When I purchased it I didn't know it actually has API built for it as pretty much everything made by google :). So I loved the device but there was something I really wanted to add to it - Person Positioning. For example: when I am in living room I want my thermostat starts hitting/cooling based off the temperature sensor which is located in living room and when I go upstairs it would change sensor to bedroom automatically.(yeah yeah HomeBee already has that feature built in but if I would go with HomeBee i would never had this fun working with my RaspberryPi and Python).
The plan was to check presence of a person in each room by using motion sensors connected through already built phone line.
Unfortunately this project had to be put on a shelf. Google decided to rebuilt their API. Still has sensor working nicely and API calls logic implemented.