Hmm I don't know anything about flashing Shibby or Tomato or DDWRT but I know that some VPN's will actually terminate traffic if they cease to be anonymous. So in other words if you were surfing and the VPN stopped covering you the VPN would terminate the packet transfers to keep your identity hidden.
Might wanna look into a paid VPN that offers that. Most paid VPN's offer PPTP, L2TP and OpenVPN. Here is a list you can use to narrow down your search:
Code:
http://www.vpnsp.com/vpn-providers.html
I would get one that operates outside the U.S. especially if you looking for using it for IKS. That would be one who's domain doesn't operate on a .COM or .ORG or .US or .NET top level domain.