Spoof, free and nothing to download
Spoof is the classic bar game for deciding who pays: everyone hides 0 to 3 coins in their fist and, taking turns, says how many they think there are in total. Here the phone is the table: you pass it around to choose your coins in secret, the calling order rotates on its own and repeated numbers aren't allowed. When the hands open the coins are counted and whoever guessed right is safe. You can also play each on your own phone by creating a room: everyone hides their coins on their own screen, the calls show up instantly on every phone and the hands open at the same time. It's quick, takes ten seconds to explain and always ends with someone buying a round.
Tips and variations
- Count your own coins: if you hide two, calling fewer than two is throwing away your turn.
- Listen to the players before you: their numbers say a lot about what's in their fists.
- Calling last is an advantage, because you already know what everyone else said.