The power wire seems to hand accessories up there just fine. I’m using it to power a 12v to 5v micro USB converter for my dash cam and also send 12v to my radar detector. It’s nice to have everything automatically power up when starting up and shutting down automatically too. No loose wires anywhere either.
Note if you do decide to mount a dash cam and radar detector dump the suction cups and use the 3M Dual Lock fastener strips (Velcro on steroids). A consumer pack is only $3 at your big box hardware outlet. It gives a nice tight and clean install up high and out of the way.