Home VPN Server App

[wallpunch]

Imagine an app that users can install from App/Play Store onto any phone or computer, then use that device as a VPN server without needing to jailbreak, root etc.

I think it would reduce the barrier to self-hosting a lot and also get around data center IP blocks.

One big issue is NAT, since devices behind a symmetrical NAT could not work as a VPN server.

Also I think it's impossible to let the app run in the background on phones, only foreground, so that may be too inconvenient.

Has this been tried before? (The closest I know of is Snowflake) Would it be helpful for getting around censorship? Are there other big issues I'm missing?