WARNING: I take no responsibility for anything that happens.
THIS GUIDE IS WRITTEN FOR A MY08 E92 BMW M3. IT MAY WORK ON OTHER MODELS AND YEARS, IT MAY NOT. USE AT YOUR OWN RISK. Edit: I have used this method on my 2011.5 M3 with no issues thus far. Take it for what it's worth, but I still take no responsibility for anything that may go wrong.
Special Thanks and credit goes to picus, bilbarstow, and E92Vancouver from E90post.com, for providing photographs much better than mine.
I apologize for the terrible iPhone pictures and the hastily written instructions. Trust me though, this is much easier than it looks.
What you will need.
*MINI*-Fuse tap kit (got mine from Autozone).
Low Amp *MINI* fuse (mine was 3 amps, from Radioshack).
Two flat head screwdrivers.
T-30 Torx Wrench (6-point star-shape).
Needle nose pliers.
Everything that comes in a *Brand-New* V1 kit (Not going to hold your hand on this if you got yours used).
Laptop or printed instructions.
Start by getting all your stuff together, and having your instructions handy. Helps to have a nice, wide open, and well-lit place to work. (I neglected this last part, shouldn't have.)
Pop open the mini fuse tap kit, and get the blue wire tap that is included in the V1 kit. Tap bottom of wire as shown.
My tap wouldn't go in at all, so I had to be extra persuasive, by means of needle nose pliers.
Take the 3-Amp (or lower) fuse, and stick it into the fuse tap.
Whole thing should look like this.
Ok, now clear out your whole glove compartment. See these little knobs in the back of your glove compartment? When they are horizontal, they are locked. Just turn them so that they are vertical, and pull the backing plate out.
Behind the backing plate, there is a fuse box guide. Use it if you need it.
~*FOR THE MY08/MY11.5 E92 M3*~, fuse slot 5 is unused ignition (circled in red). I found this somewhere on the M3post.com forum, I forget where. TAP INTO SLOT 5. (Best for our purposes, since it's unused, but is still ignition-activated, so doesn't always draw power.)
For everyone else, I have no idea, and in that case, you may consider tapping into the slot corresponded with the picture (circled in red in the photo with symbols). It's the OnStar one. Some people have also tapped into the cigarette lighter. Just remember, if you are tapping a slot that is currently in use, put in both your new fuse and the old one, as shown. Obviously, if you're tapping unused ignition slot 5 like me (FOR MY08 E92 M3) you will only need your new 3 Amp fuse, since there isn't any fuse there.
Now take your T-30 Torx wrench (6-point star-shaped one), and loosen this bolt here. DO NOT TAKE IT OUT! It was a HUGE pain in the ass getting it back in. Just loosen it enough to slip your ground (black wire) on the hardwire block behind it, and then tighten it back up.
Now, remember that wire tap that we put on the fuse tap? Plug in the red wire on the hardwire block into it, to give it power. (Above photo.)
Now, plug in your phone line into the Main Unit slot, and plug the other end into your V1.
With your car off, the unit should NOT BE ON.
But once you turn on your ignition....voila! We have power.
....Wait, it's not turning on! Oh what did I do wrong?
Don't worry, it's probably not a big deal. Go back to your fuse tap, and turn the thing 180 degrees, and plug it back in....
Bam! It should be working now. Yes, up and down direction does matter for the fuse tap. Luckily it wasn't such a big deal, huh? Phew!
(Notice the wire is pointing down in this photo now, instead of up like in the previous ones. Also notice that fuse is now facing left, and not right.)
IGNORE THIS PART IF YOU DO NOT HAVE A HIDDEN DISPLAY!
Now, plug your other phone line into the Accessory slot of your hardwire block. Then, put the backing plate into your hidden display. I slipped my phone line behind the backing plate, in these little cracks here, to make everything tidy. It'll fit.
I then shoved the cord inside the cracks of the trim, and ran it to the glove compartment. I placed my hidden display here. It didn't require any velcro or anything, since the pressure of the ashtray lid keeps it from moving around.