Yeah it would be cool to have it maybe down by the ball launch so it is out of the way but I could not see how to get it to work ingame. I tried Toper on backglass and moving to my playfield screen. Neither showed once game was launched BUT Backglass did display when browsing games in PBX. I just found that to be easily over looked as most browsing rarely look up
So I think the wheel "solution" is a decent way to approach it just requires more upfront work on editing the wheel images initially. Idea is person will see the QR code before going into game, scan and put phone down until they finish their round. then submit score.