Can it replace iTunes Match? Not really. If you trick Bonjour into finding things across the vpn you could possibly get home sharing to work. And these tricks usually only work for OSX not iOS. You are better off getting one of the Seagate's Wireless Plus drives as seen at macworld and just take it with you. Though that won’t work for iTunes DRM content like video.
Scoping of what you want to protect:
What are the risks of open wi-fi?
Basic open hotspot tips
OSX Server- http://typicalmacuser.com/wordpress/2012/01/07/tmup-252-lion-from-scratch-auto-save-versions-and-lion-server-vpn-setup/
VPN Server Configurator for Mac OS X 10.5 - 10.8, http://www.greenworldsoft.com/product-vpn-server-help.html
Back to my mac. Sometimes it works.
OpenVPN (ssl based and not iOS friendly)
can install on OSX
Linux based: Run in a VM or an old PC for switchers with those still around.
pfSense firewall (very much a network geek solution but iOS friendly)
Untangle firewall (http://hak5.org/episodes/hak5-1405)
Non VPN options that offer remote control: Logmein, Air Login
Non VPN option that offer file access: Dropbox, Transporter
($8/$15 month) Whom do you trust?
Makes a iOS profile file you just tap to add the settings to your iDevice. Very easy setup.
($4.99/month or $29.95/year)
Free with ads. Also supports non Apple OS systems.
Personally I’d go with getcloak. They are more active in the Apple community.
One other option. If you are a student or a higher ed employee it is likely you have existing VPN access back to your University at no additional cost and support for devices is extensive.
Am I safer running my own connection through my mobile phone?
For the most part yes. But it is not impossible to fake cellular towers now. The police are doing it and gathering more information than just the “bad guys.” And bad guys can do it for minimal investment. This is why I kill bluetooth, wifi and only flip on cell service in brief periods when at security conventions. It’s a juicier target than just chance encounter with someone setup for that in a public venue like a Starbucks.