Most gamers are totally familiar with the mouse/keyboard set up…and rightfully so. It's been in use by FPSers ever since Quake and other games came out allowing people to use mouselook. So, why would anyone ever want to change this?
For starters, the keyboard is rather bulky and large. Designed for two hands, and not one, the keyboard adds a lot of extra space and keys that most gamers will never use due to their device arrangement. Many people either use the number pad of the ASD key-sets on the keyboard with their left hand, while mousing with the right hand. This leaves all the rest of the keys as wasted space, and in some cases, a comfort hindrance. In the past, I've resorted to buying a separate PS/2 numpad and programming Quake to use it along with the mouse. Thanks to this, I could use a small keypad alongside the mouse and Quake much more easily. The number pad still had its problems, of course. It was small and rather flimsy, so sometimes I flipped it off my lap while using it. Also, being a numpad, it was preset with the buttons of a normal numeric keypad. If a particular game didn't support them all, I was just out of luck.
The Claw solves quite a few of these problems. Essentially, the Claw is a 9-button keyboard that fits the shape of your hand. You can use it to emulate any nine keystrokes without the need for actually having your keyboard handy. All you have to do is plug in your normal keyboard through the passthrough cable and spend a couple of minutes setting the buttons to correspond to specific keys. Once you've done this, set the Claw back to normal operating mode, open Notepad, and press some of the buttons to test it. Say you've programmed the pinky button to correspond to the 'I' key. Pressing the pinky button should show you an 'I' in Notepad. I generally did this before starting a game to make sure I had all my keypresses properly configured.