Jason from DIYdrones posted a video of the anti crash feature for ardupilot 2.7
Ardupilot is the predecessor of ArduPilot Mega. This is a smaller autopilot that is still based on the Arduino platform. Ardupilot is designed for simpler fixed wing aircraft(3 channels). Supporting autonomous stabilisation, way-point navigation, and one way telemetry with Xbee modules allows for a cost effective UAV autopilot. This board supports 4 RC channels in, and 3 out with one serial port. For stabilisation, Ardupilot supports both thermopiles or an IMU.
The development of the open source control software has slowed down since the introduction of the Ardupilot Mega UAV controller, there are still occasional updates to the stable and well tested software.