I am really excited about the ultrawideband implementation! The technology has been around for a few years now but the interface is quite complex and is hard to get up and running.
The actual ultrawideband devices (decawave) are available on digikey for $10-20 each so if a good open source implementation exists, that would be very exciting for hobby robotic makers.
I agree UWB system has good quality positioning, it's not affected by lights or smoke and it's quite cheap. The localization is processed on each Flight Control and it's integrated inside the Arudpilot firmware and passed to the Ardupilot EKF.
The actual ultrawideband devices (decawave) are available on digikey for $10-20 each so if a good open source implementation exists, that would be very exciting for hobby robotic makers.