Hi, here is few links (Chineese website). I ordered one but the shipping is not fast :I was also thinking about this system. If it will work, it could be our best bet. No interference with WiFi, no OTG cables, no additiona drain on phone and as a bonus it is lightweight!
Today I was flying slalom around trees and sometimes my fingers slipped out of the screen, which caused a lot of near misses. This would solve it all. If nobody tried it, I may order one for test. Do you have any link?