Apple only allows the use of the Magic Mouse on Apple computers with Mac OS X 10.5.8 onwards, something that has caused the anger of many people who continue with Tiger happily but who cannot enjoy the Apple mouse.
For them, the Magic Driver has come out, a third-party driver that will allow us to use the new Apple mouse in Mac OS X Tiger, and that also in the future will also allow you to use the Magic Trackpad.
You can download and test this Japanese creation on your Tiger without a problem, although I don't attest that it works since I have Snow Leopard ...
Link | Magic Driver
Source | Mac OS X Hints