So I saw that Métro had an updater program, called MétrUp which will update the program and all installed city files if run when the Palm is connected to the Internet. Looking into it, I discovered that one of the Palm networking options was to use serial! So, I checked it out and sure enough I was able to put my my Palm Pilot Vx in the cradle and route its networking through the serial connection and my computer. It was really pretty easy, and I did it following the steps at the end of this page. The “Point to Point networking on Palm” HOWTO is even more detailed, check it out if you need an explanation of a specific step or want to tweak.