accodring to this
the i.MX508 has usb host capabilities. and here comes the *but*... On Freescale's website there are schematics for a i-MX50 demo board which "fits" for allmost all i.MX508 family processors. there is also a usb host on the schematic but sadly it uses different pins then the usb otg. i am not 100% sure if this is also the case for the i.MX508 SoC but it seems so... i don't think a basic "wiring" adapter and some clever software will do the trick. even if the host pins are hooked up inside the kindle (i'dd doubt that as every hw company tryies to reduce cost even by cents and thus will not add every feature the SoC supports) we would still need an external power supply to power the external device - hosts need to do that. now please correct me if i'm wrong...
i'll check the kindle for usb host capabilities (i'll take it appart, again, to see what's on the PCB) and come back here to report my findings.
by the way, does anybody have a "schematic" for the touch. or anything that resembles one :-)