With iTunes Wi-fi sync in iOS 5, it seems that the host iTunes machine and the iOS device have to be on the same LAN. Is it possible to circumvent that requirement by accessing the user's LAN (with the host iTunes machine) via the iOS VPN? What steps would you take to set this up?
–UPDATE–
I've been researching this for nearly another hour, and the sticking point seems to be Bonjour. The clearest description of the difficulties I've seen being in this Apple support discussion:
https://discussions.apple.com/thread/1549218?start=0&tstart=0
Obviously there are ways around this with various third-party VPN solutions, but as far as I can tell, all of those require some sort of software on the client side, whereas on iOS devices, built-in support is limited to L2TP, PPTP and IPSec, none of which seem able to pass Bonjour packets.
Is there some way around this? Ideally, a solution would only require modifications on the home end of things, so you'd only need an iOS device on the remote end to make it work, but if you have a creative solution that involves a MacBook on the remote end and connecting the iOS device through that, I'd certainly be open to the idea.
Best Answer
Not a full answer but as you seem to primarily look for hints and pointers:
According to this MacOSXHints article from three years ago it seems to be possible to route Bonjour over VPN using OpenVPN or LogMeIn. This should (with some hacking and routing magic probably) at least allow WiFi syncing as long as you have computers (not iDevices) on both end of the VPN (and connect the iDevice to one of them).