GuizmoVPN (http://www.guizmovpn.com) is an OpenVPN client for the iPhone available for installation on Jailbroken devices. OpenVPN is, as its name suggests, an open source virtual private networking application, suitable for a wide range of secured comms applications. For more information read this blog article - http://blog.brightpointuk.co.uk/openvpn

The iPhone client is available for download within the Cydia manager, but must first be added to the list of available sources. Within Cydia browse to Manage --> Sources:

and add the source "http://cydia.guizmovpn.com", you will then be able to install the client.

Full installation options are available on the GuizmoVPN web site, but setup is relatively quick and painless provided you have a correctly written client configuration script. The following script worked for me:

client
dev tun
proto udp
hand-window 15
remote (server_IP_address) 1194
resolv-retry infinite
nobind
persist-key
persist-tun
ca ca.crt
cert jamesl.crt
key jamesl.key
comp-lzo
verb 3

Your script would naturally need to include the IP address of your OpenVPN server and specify the appropriate key and certificate files.

The script should be saved as a ".ovpn" file in the same directory as all required key and certificate files. The directory itself should then be compressed to a ZIP file and copied across to the iPhone.

The easiest way to do this is to connect the iPhone to an available WiFi network and upload the ZIP file to the device from your PC. Launch the GuizmoVPN client on the iPhone and select the option to enable the web server:

Provided that WiFi is enabled on the iPhone and connected to the wireless network, its local IP address will be displayed:

From your PC, or another machine on the same wireless network, open a browser and connect to the IP address of the iPhone on port number 2095, as shown in the GuizmoVPN screen, the following will be displayed in your browser window:

Browse to where the ZIP file is saved on your PC and upload it to the iPhone.
Once uploaded, the configuration will then be listed in the GuizmoVPN client:

You can now turn off the web server on the iPhone.
To initiate the connection to the OpenVPN server, simply move the Connect switch to On. If prompted for a password, enter it at the prompt. If the connection is successful, an icon will be added to the status bar at the top of the screen to represent the VPN connection:

You will now be able to access remote resources via their internal address:

If your are unsuccessful, view the log file for information and error messages to assist your troubleshooting.