AirConsole

This ideas is less of a 1 episode challenge, and more of a mini-series like the Agar.IO replica.
AirConsole is online game console - which uses phones as gamepads. Check it out at http://www.airconsole.com
What's even more special about it - You can make games for it yourself using JS. It works amazingly in conjuction of P5JS, and its also about networking, because there is a constant need of the console (browser) and the gamepads (phones) talking with each other.
It is also very developer oriented: All you need to do to test your game, is go to http://www.airconsole.com/simulator/#http://IP:PORT/
(Ip/port of your machine running a webserver) and you can easily test your game using virtual phone and connected JS console of all parts. And when your finished your game, you can submit it for review - and it can be added to the official console.
All the official documenation of the API/Guides is at http://developers.airconsole.com

This is quite different from the usual style - but it can be a cool series.