the vehicle dynamics processor may work for the gps, i got that as part of my trade for my avh-p5700... i'll see if you can add that to yours.I got to reading the manual and it has a gps sensor... its a $400 add-on and apparently very handy to have to measure vehicle schematics as well as gps etc.
ok i just checked and it does not say it works with it but it does not say it explicitly doesnt... the 4100 is a touch screen yes?
http://www.pioneerelectronics.com/PUSA/Products/CarAudioVideo/Accessories/AVG-VDP1