MySensors
MySensors is a free and open source DIY (do-it yourself) software framework for wireless IoT (Internet of Things) devices allowing devices to communicate using radio transmitters. The library was originally developed for the Arduino platform.[2][3]
The MySensors devices create a virtual radio network of nodes that automatically forms a self healing mesh like structure. Each node can relay messages for other nodes to cover greater distances using simple short range transceivers. Each node can have several sensors or actuators attached and can interact with other nodes in the network.
The radio network can consist of up to 254 nodes where one node can act as a gateway to the internet or a home automation controller. The controller adds functionality to the radio network such as id assignment and time awareness.