Within Settings in the iOS app on your device, you can supply an additional, internet-facing IP address for your TouchControl Server(s), and TouchControl will automatically detect the network state and use the best connection available (i.e. WiFi if it is available, and 3G/WWan if it is not).
Within Settings, select your TouchControl Server (under "Network Settings"), then tap the "Edit" button on the nav bar, and enter your Internet-facing IP address in the "3G Server" field. You can use the "Find it for me" button if you are within your server's home network, and it will attempt to detect your Internet-facing IP address and enter it into the field for you.
If you use a dynamic domain name service (such as DynDNS or Windows Home Server DNS service), you may enter your DNS hostname instead of an IP address in this field.
If there is an IP address or host name entered in this field, TouchControl will attempt to use it whenever the device does not have a WiFi connection available. On the main settings screen, you can also turn on the "Force 3G" option, which will force TouchControl to use the "3G Server" address or host name, even when on a WiFi connection. This is useful when you want to use a public WiFi hotspot such as at a coffee shop or hotel. Note that in this situation it is not truly forcing 3G connectivity, it is simply forcing TouchControl to use the “3G Server” address to connect to the server.