Well, all you'd need to do is run a cable under the centre plastic cover, down the side of the gear gaiter and then up the arm-rest.
You'd need to drill a hole in the bottom of the arm-rest for the cable, plus somehow route it through the arm-rest rotation mechanism (probably the most difficult part). The centre console can be removed/loosened by just undoing the screws on the side of it (under small plastic covers) and IIRC couple of bolts under the rubber mats. You would need to remove the gear gaiter surround to get better access.
I placed my iPod in the glove box as it's the easiest place to use, out of sight and still easy to access to take it out if needed. The amount of work needed to install it into the arm-rest is not worth it in my opinion.
