There are a couple of ways to set one up. If you have an old Android phone that is rooted, you can use it. Otherwise there are devices you can buy for around $50. One who tried it at a convention said that he saw several people connecting and that attendants were going around trying to figure where the signal was the strongest to try and locate the box.
That made me laugh and I wouldn't mind trying that. I like the old Android phone idea. 1. They can't search you and 2. Good liking finding it. The signal is the same up to 50 ft and a 50ft radius at an assembly or convention could be 100's of people. Plus, act like you're taking notes and nod your head after everything the speaker says. You'll be the least suspected verse some teenage kid looking like he wants to shoot himself.