A company called Digital Convergence came out a couple of months ago with a nifty little barcode scanner called the :Cue:Cat. They have generously agreed to give it away free through RadioShacks everywhere and subscriptions to Wired and Forbes. Unfortunately, they found out that geeks around the US were getting their hands on 'Cats and refusing to use them for the bovine e-commerce-grazing, demographics-harvesting use they wanted them put to, and threw a hissy fit.
It is my (IANAL) opinion that their arguments regarding intellectual property, etc. are blowing smoke in order to protect their rather poorly-thought-out business model. For you see, you give a geek a toy, you'll get a couple of zillion uses. And I got no problem stomping on them, because of a little thing called fair use. Their license agreement claims ownership of my CueCat? I don't think so. I signed no contract. I was not told this was a "rental". *My* 'Cat, to do as I wish with it. I talked it over with a lawyer, so I feel confident ranting like this.
I won't rehash information available in other locations (flyingbuttmonkeys.com, for example). The CueCat is a fairly simple barcode scanner, capable of handling most of the basic barcode designs (though it doesn't do the 2D codes such as UPS uses for shipping). It bounces light from a red LED (not a laser) off the surface of the scanned object, decodes the barcode, then sends it back to the computer in a form that only Digital Convergence is supposed to be able to read. This encryption scheme has of course proven to be shot through with holes and it's fairly trivial to turn the CueCat into a general purpose bar code reader.
The other slightly interesting point is that the standard PS/2 CueCat plugs into your keyboard port and acts as a "keyboard wedge", i.e. a device that plugs inline with the keyboard and emulates its behavior. If you don't have a specialized driver for the 'Cat on your system, it will simply feed the encrypted output stream directly to whatever is currently passing for a keyboard interface on your system. This makes hacking around with CueCat output especially easy to deal with.
Note for Mac users: You may have seen MacCat, a program designed to handle CueCat input on a Mac clone (the anonymous author used a Power Computing box) with a PS/2 keyboard input. I haven't tried the software, but I did manage to finagle a USB CueCat from a local RadioShack. Now technically you're only supposed to get these things if you buy a new Compaq from them, but the manager of the store just got it for me. Sad, really; he wasn't even greedy enough to give me the chance to offer a bribe. It was just no fun. Anyway, according to Apple System Profiler, the 'Cat looks just like a USB keyboard to the system (no surprise there), so it behaves precisely as the original does.
Digital Convergence is in the demographics business, not the scanner business. You're always free to do it their way, if you don't mind the fact that they're tracking you by the serial number in the 'Cat's output. It's also been used for cataloging books by ISBN.
I do have a couple of interesting ideas for what can be done with it, though; you decide whether they're useful to you and let me know.