Time Bomb: do the task, pass it on, fast
One phone for the whole group — and that phone is the bomb. A task appears, whoever is holding it does it, taps done, and hands it to the next person. Nobody knows when it goes off. Whoever is holding it then loses the round.
Fuse length
At least
At most
It goes off at a random moment inside this range. The screen never shows how long is left.
Tasks
Do the thing on screen, tap Done, then hand the phone over.