I mount my DC's on a magnet from a dead hard drive. It's glued to the dashboard with double-sided 3M adhesive tape used to hold plastic door moldings in place. Another magnet I have glued to the bottom of my cams.
From the outside it looks like this (GS2000 is in the center of the photo).
Installing and removing DC is a cinch, all buttons are within reach, screen clearly visible when needed. Screen saver is set to 120 seconds so it doesn't distract when driving.
The cam doesn't obstruct visibility. All it blocks from view is part of the bonnet.
As for wiring it goes like this. Switch on the dashboard is connected to a fused constant 12 volts source. The wire goes inside the dashboard...
... under the shelf below the glove box to a 12V to 5V converter I have bought on eBay from supermario-au for a couple of dollars...
... put into the coolest spot I could find around the center console without taking the interior apart.
The shelf has rigidity elements on the back and the module fits into one of them nicely.
5V output cable goes back alongside the 12V feed wire and comes out on the passenger side of center console.
I hide the USB cable in the gap between console and shelf when I remove the cam and leave the car. Magnet on the dashboard doesn't stand out too much because I have covered it with a bit of thin black insulation tape.
The car is a MkII VW Golf.