Originally Posted by worwig
...The challenge for me is getting a screen that is visible in sunlight, modifying gloves to work with the touch screen, and the waterproofing...
high-contrast black/white maps help a lot more than you would expect them to. Definitely worth a try. A sunshade helps as well and does protect from the elements somewhat, but it can be awkward to work around.
Other than that... I probably won't get around to trying this, not before truly daylight-readable screens are cheap, but I've been thinking about using an e-book reader as a remote screen. Basically, pick up a cheap monochrome e-ink tablet and figure out a way to display a picture, once per second. The same picture, over and over again. Then, update that picture by screen-caps on the actual GPS tablet.
The actual GPS could be small, protected (though you'd still need it for touch-screen controls), and the display wouldn't really matter. The e-ink display, on the other hand, could be mounted in a protective case (that you wouldn't need to open all the time) and be fully readable (even more readable) in direct sunlight. No sunscreen, big, and depending on how good the look-angle is it might even be mountable directly on the windscreen. Those e-book readers can get pretty thin and light.
A once-per-second update, or even 3 or 4 seconds, would be fine for displaying a map. I ride fast, but not THAT fast. Getting a small app to grab a screen-cap and post it to a file once per second would be trivial. Getting the e-book reader to see that file (USB, bluetooth, or ?) and display it might prove a little more challenging. However, I do think the idea has merit. I just don't have the time to do it and my high-contrast maps are actually good enough for my navigation needs. Not awesome like e-ink would be, but good enough.