Welcome to the forums!
With release 4.0 of the UNIStim firmware for the 1140e there is a built-in VPN client. It's referred to as the UNIStim VPN Client (UVC).
You can find some of the information on this blog post;
http://blog.michaelfmcnamara.com/2009/12/unistim-firmware-release-4-0-for-nortel-ip-phones/Good Luck!