Ideas

An app or feature that is focused on get-togethers (i.e. MeetUp) that require a specific number of people or specific intervals of people. For example, a volleyball / tennis group that wants people in groups of 4, or pickup basketball that would require between 10 and 13 people. Ideally would be integrated into iMessage/What's App.

An app that tracks personal grudge scoreboards (e.g. husband vs wife chores or crossword speed) over time. Ideallly would integrate with other sources of data for easy result reporting. Notifications to opponent(s) when a score is added/updated. iMessage/What's App integration for shit-talking.

Single-purpose horizontal selfie flipper for iOS. Should work on batches of selfies too. Make sure flipped selfies are saved as Selfies or Portraits in iOS if applicable.

Recipe manager whose distinguishing feature is that it can be voice controlled so that you don't have to keep touching the screen with food soiled hands. Would also work for DIY projects that don't involve cooking.