Of course I (and the OP) can build one ourselves... but I want one that's easy to use. Ideally, just plug it in and configure its wifi access, and create some k

Of course I (and the OP) can build one ourselves... but I want one that's easy to use. Ideally, just plug it in and configure its wifi access, and create some kind of "peer group" for it that my friends can join remotely with their own devices. Then everyone in my peer group gets an encrypted backup of my files, and I get an encrypted backup of theirs. The main difficulty will be making sure this baby has seriously expandable storage. I have terabytes of stuff to back up. So do the people I want to connect to. This thing needs to scale up to 10-20TB min to be useful today.