This kit comes with all the receivers and hardware necessary to turn just about any in-car display into a navigational unit. I don’t even think it has to be a touch-screen since this kit comes with a remote that could control the software.
There is the initial unit that has all the hardware in it, such as the 300MHz processor, the SiRF Start III GPS chipset, and the 2GB SD card that holds all the maps and such. Then there is an external GPS antenna, an external speaker, and an external IR sensor as well as the remote.
The GPS antenna is obviously so you can get some decent reception while still maintaining the ability to hide everything else, then the speaker is so the device can give voice directions, and then the IR sensor is so the remote control will work. It will support up to a 430×234 resolution display at up to 16-bit color and a 16:9 aspect ratio, no word on price or availability, but its from a Hungarian company, so it might not be intended for the US.