Environmental sensor
From Kerbal Space Program Wiki
Environmental Sensors Environmental Sensors are a set of parts that may be implemented in .18. At this stege they seem to consist of Accelerometers (Instruments to measure acceleration) and Thermometers(Instruments to measure heat). They will probably be in the Utility&Scientific section of the construction menu.
Here is a video showing them being used on a probe by NovaSilisko: http://www.youtube.com/watch?feature=player_embedded&v=oXzNo4KYulA