A lot of sports require more than one person to play such as football, tennis, basketball etc, but it's often difficult to organise a game within our social circles as everyone is busy. However, we don't necessarily need to limit finding sport partners within our social circle, we could play with anyone who's interested in the sport and playing with new people can also help us make new friends.
This iOS app would have two main features: 1. Organise a new sport activity, define how many people you need, where it would take place, any fees to be aware of, etc and wait until people start requesting to join. If more people want to join than needed, you can choose which players you wish to accept based on their profile. The leftovers won't be left alone, the app will suggest them to organise their own game.
Once you have your team, you can start chatting in the app to discuss further details.
2. Join any upcoming sport games in your area. You can filter by location, time of event and even sport. Once you found a game you're interested in, you can request to join. Be sure to have a profile picture and details about your sport levels on your profile page.
In addition, the app could have further features that resemble a social network such as: - Adding friends - Making posts - Following friends
Technical details: The iOS app would be written in Swift (native) and I would also build a custom backend for this project in Flask(or something similar), I would use SQL or NoSQL for the database and I would make sure the system is secure using techniques such as tokens, two factor authorisation and encryption of sensitive data.