pfSense

I would like to see implemented a feature to use an USB 3G modems as a failover (not balancing) dial-up connection (connected only for the time strictly needed) to be used as in a Gateway Group.
A 3G failover connection always on is completely useless if you have a contract charged on a time basis (almost all 3G contract in Italy are charged according to the time you stay connected).
Actually it is not possible due to the way gateways are monitored in the "Gateway Groups".

In other words, using this feature you should be able to configure your box with a primary ADSL connection and a 3G failover working in this way:
shutting down the primary Wan (ADSL), the 3G modem should become active (dial up) and the traffic should be routed through the 3G connection.
When the primary ADSL connection comes up again, the 3G modem should disconnect and the traffic should be routed again through the ADSL connection.