The Tidmarsh sensor node is a low-power wireless sensing platform. It contains an 8 bit microcontroller, 802.15.4 wireless and a set of environmental sensors. It can run for several years from non-rechargable batteries and report sensor data several times per minute. Now what these guys at MIT did, they connected the RPI to the sensor node of Tidmarsh and got you did really cool DIY.
You can now order the pi to capture an image and do cool things with that, like tell you the temperature, humidity, pressure, luminance and of course, share it on Twitter. You can get all the configurations and commands in the source link, given below.
Trying this, is highly recommended.