Fun idea for a todo list app: Suicide Pact.
(Requires at least 2 people to play.)
1. Each person selects one task that needs doing.
2. When everyone’s accomplished their task, there’s a “group win” event – everyone gets points. Critically, you DON’T get points unless everyone does the task.
3. When everyone’s accomplished their task except you, you’re gonna feel the pressure, and people are probably going to harass you about it so they can trigger the group win rewards.
4. Leaderboards, so some people in the group are visibly ahead of others.
5. Save-a-friend: Allow some people to do extra tasks to save a friend from slipping on their task. This might have to be limited.
(This dynamic is present in military boot camps and in MMOs like World of Warcraft)