All currently shipping Macs (with the exception of the Xserve) come with an Apple Remote free of charge! What a deal. As you know the tiny white Apple Remote lets you control Front Row, and when coupled with some third party apps lets you do even more.
Sik looked at the Apple Remote and thought, 'Sure that's cool, but what if you could store that remote in an ExpressCard slot, like those found on the MacBook Pro?' Hence the birth of Rex, a replacement for the Apple Remote that is capable of doing everything the Apple Remote does, and can be stowed in your MacBook Pro's ExpressCard slot.
The remote is $26.