The idea is to use try to use NAT traversal (i.e. STUN or UPnP) to get a direct connection, and otherwise relay (i.e. TURN) with end-to-end encryption. I'm hoping IPv6 will eventually allow direct connections everywhere so nothing needs to be relayed.

I haven't built that stuff yet though so the current version requires that your home computer has a public IP address and that you open a port in your router. Obviously it's only usable by technical people right now, but I do eventually want this to be something my mom can install and use on her own.

Check out zerotier; I've been looking at similar p2p techniques and ZT does a good job of packaging them all up with a relaying fallback.