Pick a question. Participants join via qr code and give an answer. Once the game has started, everyone is given their own qr code. When you scan someone's qr code you see their answer and are given 30 seconds to chat about it. When the game is stopped there is a quiz, you have to match up all the people you've met with their answer. Whoever gets the most people matched wins!
Meetup is broken up into random teams of 9. Each person is given a square in a 3x3 image which appears on their phone. They have to find all 8 of their teammates and arrange their phones into the correct image. Fastest team wins.