Is it even possible to do push notifications without relying on a centralized system (Google, Apple, or whoever)? Sounds like a very difficult problem to solve while preventing privacy leaks, spamming, DOS attacks and still being reliable and globally available. Who would pay for the infrastructure?
(Please, no 'blockchain will solve this' answers!)
Doing it without killing battery life is... challenging. There are good non-user-hostile reasons it's centralized. Google was a bit wild-west about it for a while and lots of Android apps used custom push services, and the results weren't great.
It's a very difficult problem, no doubt. Implementations are currently battery-constrained, hence the usefulness of GCM/APN for efficiently batched polling. I suspect a fully decentralized system could be feasible for use cases that can tolerate higher latency.
- The ability to send push notifications without replying on GCM/APN
- Support for mesh networking (multiple low power peer connections)
- Convenient "lockdown" mode that encrypts your phone's contents for international travel
- Included hardware wallet/keystore for signing all data that you upload to social media