So Day One (the journaling app I use) stopped syncing between devices a couple of days ago:
http://help.dayoneapp.com/day-one-sync/sync-status
It's surprising how inconvenienced I am by that—notes I've created since Monday are distributed on three devices and I'm surprisingly annoyed I can't find notes 2/3rd of the time when I reach for a given device.
P2P/decentralized lesson: even if data is stored locally on devices (like Day One does), let devices sync by themselves (ScuttleButt takes this idea to the extreme).