Small phillips head screwdriver
Soldering iron and solder
Small microphone (I salvaged mine from an old headset)
A small drill.
Step 1: Take the Back Cover Off and Locate the Solder Point.
Step 2: Get Your Microphone Ready and Drill Some Holes.
Step 3: Mount and Solder Your Microphone.
Step 4: Close Her Up and Turn Her On.
(The only map version of Navigon that works with voice recognition in the US is 2008 Q3. You must have that map and the corresponding phoneme.nfs file.)
Note: Ignore the red and white wires I have hanging out next to the gps receiver in the photos. That's for an automatic power on mod that will be coming soon.