Which tech is recommended to write P2P mobile apps?

The "task list" app is a common example app for many web-frameworks, but I haven't seen a P2P mobile app out there. F-Droid ( https://search.f-droid.org/?q=p2p+task ) and the playstore ( https://play.google.com/store/search?q=p2p%20task&c=apps ) don't have any results.

I have no experience writing mobile apps, because GUIs aren't my thing and the android emulator is way too heavy. I won't shy away from Java or Javascript if they make my life easier, but my major problem is I have no idea how to write P2P apps.

So, what can I use to write a simple, lightweight, P2P, mobile task-list/todo-list app?