An idea for a free, open-source E2EE contacts sync (No Internet permission required) - Would you use this?

Hey everyone, I wanted to share an idea and get your thoughts.

Lately, I’ve been decentralizing the services I use. I’m using Proton for mail and docs, Ente for photos, etc. I’m not completely de-Googling just yet, but I strongly prefer not having all my eggs in one basket.

The one gap I couldn't find a good, simple replacement for is cloud contact sync. The main alternative I found was EteSync. It's a great project, but it wasn't the most convenient for my workflow, and honestly, paying a subscription just to sync my phonebook felt a bit much for such a basic task.

So, I started thinking and came up with an interesting solution. I’m already past the PoC stage.

I've built a way to continuously and securely sync my contacts to any cloud of my choice. It uses true End-to-End Encryption (AES-256-GCM) where the key never leaves the device. But here is the most interesting part:

The app requires ZERO internet permissions.

The only permission it requests is access to your contacts. It cleverly leverages a native infrastructure we all already have running in the background on our Android devices to handle the actual sync. Naturally, it will also support standard VCF import/export.

I’m building this primarily for myself right now. But if there's interest in the community, I will polish it, release it completely Open Source (FOSS), and it will be completely free, forever.

What do you think? Is this something you would be interested in using?