When I'm connected to an unsecured wireless AP (coffee shop for example), I want to limit my computer to only sending traffic through my VPN connection. When I'm connected to the VPN, this is generally the case. However, occasionally the VPN will disconnect if there's a wireless dropout, etc. In this case, I don't want the computer to silently start sending unencrypted packets over the air.
The rule is: If connected through an unsecured wireless connection then only allow VPN traffic. When I connect to the VPN, obviously other traffic would automatically be allowed because it acts as an additional WAN connection.
Operating system is Windows 7 x64 RTM.