There’s some nostr experiments to embed a relay in to the mobile app right? And I think amethyst has done something making the mobile app a nip-46 remote signer.
nostr:note1s2h2k9f7eut0cvg6dr5yl3njc6ns2yg9c5k9lm5gg04h86nn5u4qypkrv6
Discussion
Just storing data in a custom format that suits your app needs is probably better.
https://github.com/greenart7c3/Citrine
Citrine is the relay. There's a lot of work to do on configuration and the ui but already works as a local relay.
And amber is the signer.