I know this will sound funny but you could always crack open the RF remote for a fan (for example) and use a processors on board relay to manually connect the two normally open connections on the board to simulate pressing the button.

The same goes for your garage door manual button(s). There simply two wires that need to be connected for the doors to open / close via on board AMX / Crestron relays. Run one of the wires through a normally closed manual switch attached to a bracket so when the garage door is open the loop cannot be completed. This will assure the door can never be closed remotely, only opened.

The bracket / switch has to be at the bottom of the door so even if the door is open an inch, it cannot be closed as the loop is now severed.

We have used the I/O ports on the back of the AMX processors for this very purpose and also for feedback to the panel to let you know the garage door is currently open or closed. The feedback can also be used to show / hide buttons in AMX so unless the door is closed, the button doesn't exist on the panel.