Bittorrent had something like this with an app called Bleep. Peer to peer, no central server, and messages could have timer or simply dissappear after being read. Was a very interesting program and technology which they appeared to have abandoned. I think the way notifications and dns routing works it was just too difficult to make it appealing to the average user. Real shame.
@Phaserune sounds interesting.
The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!