While tinkering with my unit I found an easy and quick way to add a microphone to this deaf unit. With a microphone, you will be able to take advantage of voice recognition for navigation. It will involve a small amount of soldering but almost anyone will be able to do this. What you will need:
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.
The back cover has four screws. Remove those, and disconnect the battery and speaker from the main board. Set aside the back cover. On the main board, locate the area underneath the gps receiver and to the left of the sd card slot marked "mic1", and take note of the two traces with solder on them directly to the left of "mic1". There may be a sticker there that you have to peel off.