"This can only work in an area with weak cell signals"
So a music festival, then. As described in article. Where the concentration of people in a relatively small area is too big a job for the local cell infrastructure.
Though to be honest in my experience the bigger problem faced at events is battery life. It's quite funny watching half a dozen people fight over the single proprietary apple connector at a charging point and then being given evil looks as you waltz up with your phone with a standard connector and have so many to choose from...
The point being "connection" is a luxury if you can't take the pictures in the first place. So if you really want to annoy people, have exactly one apple connector at the event and set up a coffee shop nearby to watch the fallout. (I am in no way thinking of Big Feastival 2015 where there was a Lavazza stall that had done exactly this, honest)