TinyOS

TinyOS is an open source, BSD-licensed operating system designed for low-power wireless devices, such as those used in sensor networks, ubiquitious computing, personal area networks, smart buildings, and smart meters.
TinyOS is an open-source operating system designed for wireless embedded sensor networks.

It features a component-based architecture which enables rapid innovation and implementation while minimizing code and data size. A worldwide group of developers and users from industry and academia maintain and extend TinyOS.