In every smart toaster, fridge, lightbulb, lock and thermostat, there is some kind of underlying system that allows those devices to communicate with your smartphone, tablet and each other. Google wants to improve and standardize that system using Project Brillo.
Project Brillo is a stripped down version of Android with only the basic functions needed for smart devices to connect to the world around them. Along with Bluetooth and Wi-Fi connectivity, Project Brillo will support Weave, a common language already being used by connected devices and supported outside of Brillo.
Smart devices that use Project Brillo will easily connect to other Android devices without any fuss or overly complicated setup processes. Google has announced that Project Brillo is coming in Q3 2015.