Long time ago I've used Airbeam than swtiched to ndi (creating a wi-fi with password with mac, but now I don't remember if you could have that function since I am not using from a long time, as far as I rember the removed that put in again but I think you can only make an open wi-fi but maybe I am wrong).
But as Arvol said I a crowded environment is not gonna work.
Another solution could be to have an apple tv connected with a capture card to resolume and than sharing the screen (of course you need a video app in which you could remove the overlay or if you use the defaul camera app you could crop a bit)
It depends how mission critical is it because even with the apple I experience some issues.
(the apple tv is on stage, the iphone/ipad is on stage and they are also in the line of sight, and then the feed is transmitted to foh thought fiber converter, but still sometimes the communication between iphone and apple tv fall).
(of course in this case you need to associate every iphone to his apple tv)
I don't know about android