Actually, it's kind of a funny joke. I was never even aware of such a thing until I began searching to buy a PDA. I went to download sites and found dozens of listings for "mirror" programs.
What they do is completely black out the screen while the system is on (the equivalent of when the Axim is turned off). The complement of these are "flashlight" programs, which light up the entire screen (which works with backlight systems but I'm not sure it works with an Axim... haven't tried it yet). Whatever... pretty expensive mirror or flashlight, dontcha think? But then, if you've ever needed a mirror or flashlight and didn't have one handy... (who carries around such things?) then the PDA that we do carry around can come in handy. So it's not so silly as it appears at first glance. But there are bigagillions of these programs out there.
Anyway, these are extremely simple-to-write programs, thus the proliferation. It just made me chuckle when I noticed that a case company was actually including a real mirror in their case.