You can set preconditioning via i-Drive before you leave the car, but you have to set the time when you want it turned on before you lock the car.
The benefit of preconditioning via the remote app is that you are supposed to be able to turn on preconditioning as you are returning to your car and want to have it cooled down a bit before you get there.
My remote app allows me to send addresses to the nav, to lock/unlock the car, flash the lights, and beep the horn. It also will locate the car if you forget where you parked it (my wife uses that).
The commands sometimes take a long time (like 5 to 10 minutes or more) to work, but I've noticed that it seems to be working more quickly recently.