The pain point of your solution is data security. Not in the sense of it being vulnerable to surveillance or digital theft, but what happens if someone breaks in and steals your little black box, or if the house burns down? Syncing it to a CloudBased service kind of breaks the concept. One possible solution I can think of is to allow people to store encrypted copies of oneanothers black boxes. Imagine that your black…
Provide multiple ways for people to choose to push encrypted blobs to other services... Dump an encrypted blob to a dropbox account, pay this service for an AWS box to push a blob to. There are many many ways to devise secure backup - the issue is bandwidth. You'd likely have to have several blobs: pics, files, info. Pics and files are going to be huge. The service can exist in multiple modes: a physical appliance, a…
Otherwise, you might aswell just provide a service like facebook, or whatever else you're trying to replace, and offer people to encrypt their files on upload, if they do not with them to be public.
But I might just have missed the idea :-)