TextDeck is memo app which use shared text file as backend.
This app mainly assume Google Drive as a cloud storage, but any cloud storage which behave as ContentProvider is usable (if you don't understand what this means, just use Google Drive).

Just save memo and automatically synced to cloud storage thanks to Content Provider mechanism.

This app split text file by empty line, and treat each block as deck.
Just use normal text file means you can easily view and edit your memo from PC.

All sync work is outsourced via content-provider mechanism. So this app require no internet and storage permission, and many great cloud app feature, including graceful offline behavior, is perfectly available.