Just updated a project of my own that uses giftwrapped DMs and NIP44 encrypted messages and files via Blossom.
It's a Pushbullet clone, but improved in almost every way.
Android and Firefox extension are the focus but it's run on iOS and Chrome.
Working on background mobile notifications, which is harder without servers.
https://gittr.space/npub19at4nqjjymca2lh3v546vcg5ktun3al4c5xu2pts3ewckv0y70ys0gupzr/pushstr