It's my understanding that everyone on the same Wifi protocol has full access to each other host that it is connected to.
Is there any Wifi technology that allows for partitioning and isolation of each individual client... at Layer 2?
Ideally this will work even when everyone knows what the shared secret is.
I'm thinking that once a "normal" wifi session is set up, a tunnel of some sort would be enabled on the Wifi router itself to the client. Perhaps the key exchange used in HTTPS could be ported to Wifi to allow this tunnel to be created.