[leggomylibro]

Maybe have them write their numbers down and put them in a hat? Or hey, this is 2019, have them connect to a website or bluetooth beacon and enter a number on their phone?

Ooh, or I bet you could make a 10-digit keypad that wirelessly reports to a nearby Raspberry Pi for $2-5 in parts, sort of like those 'clickers' that universities use to quiz large lecture classes.

It's too bad that most cheap radio modules are so short-range, because it would be interesting to make something like that and nail them to telephone poles with notes asking people to press a button. You'd have to control for people doing things like hammering the same button repeatedly for a laugh, but it would be fun to see what happened.

Would you be allowed to use HAM bands in the US for that sort of thing if you made them like beacons which sent a callsign after the number value and device ID?

[cbsks]

If you are picking numbers from a hat, why not just put in ten numbers and pick one?

[hxtk]

Here, we see the difference between scientists and engineers ;)

[leggomylibro]

Well, each group of two could use their own hat. Or they could just write the numbers down instead of saying it. I dunno, the point is they don't have to say them out loud.

[sansnomme]

Just use the unlicensed ISM bands.