During his countless E3 discussions, Nintendo's Shigeru Miyamoto mentioned the possibility for Punch-Out! Wii.
Speaking to IGN in a short video interview, the Mario creator explains the differences between your bog-standard Wii remote and the brand-spanking new addition of Motionplus. Using Punch-Out! As an example, he notes how a far more accurate boxing simulation could be created that goes beyond the simplicities of Wii Sports.
The Wii remote itself is good at detecting larger movements, whereas the Wii MotionPlus is better at detecting more subtle movements. And so, by combining the two of those, the feeling is that it just opens up the pallette of what can be done, in terms of motion control. And so that means there's a lot of possibility in terms of something, like a very accurate version of Punch-Out!! that goes beyond what Wii Sports Boxing can do, or even other ideas...
Thanks to Kombo for the tip.