Back in 2005, Google offered "Google Secure Access", a short-lived service to provide secure VPN access across insecure Wi-Fi networks. I'm unsure why Google dropped the service so quickly, but there is still probably a good business opportunity in this space. Business travelers stuck using airports' insecure Wi-Fi and hotels' captive portals might be eager to pay for turnkey VPN tunnels. Like this blog post suggests, you could spin up EC2 proxies as on demand.
* September 2005: Google Secure Access goes beta: http://lifehacker.com/126454/google-secure-access-+-encrypt-...
* October 2005: Google Secure Access shuts down: http://www.zdnet.com/blog/google/google-secure-access-is-his...