I am exploring that stuff too.
I got a old Pocket PC from a co-worker with 32MB memory
and a cable from there http://www.pc-mobile.net/
They've got pretty much any cable you need.
you may look into this too.
That works for sure for Tracklog/routes/waypoints.
I am still learning for maps.
WANT TO BUY - KTM 950/990 ADV or SE - Projects, issues, cosmetic damage very welcome.
Possibly considering a BMW F800GS
Yamaha Majesty '08
KTM 690 Enduro '10