Bluetooth is a common addition for guys on here to add to their cars. Personally i purchased a 2010 Mk6 Golf GTI without Bluetooth and purchased a 9wZ Bluetooth (the premium version - as their is a cheaper basic Bluetooth unit as well) kit from a Sydney seller on ebay.

As long as you are somewhat handy and have some VW specific tools (torx bits and triple square bits etc) you can self-install the Bluetooth kit in under an hour. I unbolted my drivers seat (not necessary but i took the opportunity to give it all a good vacuum) to mount the Bluetooth module underneath on the carpet, then you run the wiring through the holes in the carpet up along the center console and up behind the radio. Remove the radio temporarily to plug in the loom. Then you have to run the microphone up the A pillar, under the roof lining and into the area where your interior lights are. There is a spot in there where the microphone goes.

All done in under an hour, all nice and neat (no wires visible etc and no hacking of wires) and worked perfectly.

The more advanced guys have done such things like retrofitting the reverse camera, and the xenon headlights too.