We mounted a GPS receiver, an XBee radio, and a BeagleBone board an S500 frame quadcopter with a Pixhawk flight controller, and we used Mission Planner to have the Pixhawk repeatedly fly a precise path and land on 2ft by 2ft pads. This is the same mission as the multiple landings demonstration, but with a pole to fly around.
No modification to the ArduCopter firmware, no collision avoidance sensor: just high-precision positions as calculated by SEReNa.
We are collaborating with Up Sonder on this effort.