Maybe I'll make something to talk directly to your node with RPC so I can use extended public keys to derivate addresses without the risk of exposing it (and read data directly, without limitations). (I'm thinking about the umbrel app store for exemple)
I also use their websocket api to live update the transactions.
I also use their websocket api to live update the transactions.
Bitcoin Core doesn't have index of address, so it'll be challenging task unless the input is changed to both address and any TXID which contain that address (assuming the local node enable txindex).
I'm not sure yet how to do the index part. If I can use an external one like electrum's index (because I have a node running electrum) but I don't know if it can help. Maybe I can use an external tool to index it myself but that would require extra space :/
Using Electrum protocol is probably best option since,
1. User isn't required to run their own server.
2. There are many implementation of Electrum server.
3. The protocol have decent documentation (https://electrumx-spesmilo.readthedocs.io/en/latest/protocol.html)
I'll probably make it open source yeah 
Great
.