As I wanted an better GPS Mouse for the pRoToTyPe, I did buy an iGPS M Pro USB Mouse ( http://www.transystem.com.tw/products/index_detail.php?mcat_no=2&cat_no=32&pno=10&ver=en ). I was certain that I could resolder it to Serial and use it on the Fonera Router. And thats how I did it: I did open up the Case, which was very easy, just unsnap it. You will find an socket were 4 wires do run out: Black (GND), Red (5V+), White (USB Data) and Green (USB Data) - I did cut these Wires and soldered them to an 8 Wire Cable. From the other 4 left Wires I did use only two: Under the Metal Shielding of the Mouse you will find an TX and an RX Solder Point - these are RS232 Connection Points. I did just pry open a bit of the shielding to run two wires into it, soldered it onto the points and did close the casing again. On the other end of the cable, I did solder on an RS232 Connector, Female. I did use the pRoToTyPe scheme with Phantom Power for that. Additionally, I did wire up Power and Ground a second Time to an USB Connector as well as the USB Datalines. So I have one RS232 Socket and one USB Connector and can use the Mouse for both occasions.
Hint: Do check first the Datalines of the USB Connector and the Socket so that you're sure you will resolder the USB Data Lines again in correct order.