On Android we have:
1. Pokey that people can install to be notified and that seems to be working extremely well. 

https://github.com/koalasat/pokey

2. I made a quick push to generalize notification providers
 https://github.com/nostr-protocol/nips/pull/1528

3. Amethyst implements a super simple relay watcher and sends it via Google Play Services and Unified Push. 

https://github.com/vitorpamplona/amethyst-push-notif-server

 

 Am I directionally correct here: a client publishes a nip-97 event with the push token and then a relay or some server that wants to send a push notif fetches the nip97 event for the npub they want and gets their push token out of it? 

 You send the event in the body of a POST call to the service of preference. The service then connects to those relays and sends the events themselves down via Push Services, like Google/Apple/Unified Push. 

The 10097 kind just registers which services the user would like to use for push.