The PX4 autopilot is an amazing open source platform for research. It is one of the first open source autopilots capable of running an on-board extended kalman filter and other advanced control and navigation algorithms. It is also mass produced by 3D Robotics and very affordable.
BlinkM driver with system supervision
Recently I have implemented a optical system supervision with a BlinkM or as an alternate the CYZ_RGB Firmware if you want to build your BlinkM alternate by yourself.
With this driver you are able to get an optical Feedback about the number of used Satellites (if a GPS-Receiver is mounted), selected Flight-Mode, battery warnings and alerts.
For more Information on how to use this, visit the PX4 BlinkM driver page