03+ trucks have (optional, i believe) power fold mirrors.
Folding in/out when you want them to can be done, but you will have to go straight to the motor wires, and you would have to use something, such as a DEI 528t timer relay, that would ouput for the amout of time it takes the mirrors to fold in/out..roughly 3-4 seconds, depending on age/condition of the motor.
In addition, you would have to run 2 timer relays, or 2 outputs, since polarity is reversed for folding out as opposed to folding in. If you have ever messed with or wired up window motors, its the same concept. You have 2 wires; when you give one power and the other ground, the window goes up. Reverse the power/ground on those 2 wires, window goes down.
I used the door lock/unlock outputs of my aftermarket alarm, along with the above mentioned timer relay, so they will fold in with arm, and fold out with disarm.
Also, wiring straight to the motor wires is the only way to do it. When you fold them in with the OEM button, the DDM (drivers door module) sends a signal via the databus to the motors. Since that is GM proprietary info, there is no way around it.
I was initially worried that I would prematurely wear out the motors with the daily and constant folding in/out, but I have wired them up this way for about 3 years with no problems yet.