This is just a standard ArduPilot Mega 2.6 multirotor build with the addition of an ESP8266 module for wireless loading of firmware and streaming data during calibration processes. The end result will be a fully autonomous quadcopter running of APM2.6 using the S500 frame.
The S500 frame is essentially a clone of the DJI F450 flamewheel with a few upgrades. The arms have been updated to have more screws and points of attachement to the PCB frame, and the arms have carbon fiber rods running through the. Overall the S500 is a massive improvement over the F450 as far as rigidity and stability are concerned. These frames also come in a few colors, have cheap parts (replacement after crashing), and are not very expensive at all. You can also get these frames through HobbyKing. Its worth noting that the S500 and F450 flamewheel are both about the same size and the Phantom series quads, so you can get an idea of how big it is from that.