A Better "Genius" Button

The MT3G Slide has a "genius" button, but it seems to get lackluster reviews (perhaps another example that having a really slick name is half the battle in marketing). I have an idea for Genius Button 2.0. Every smartphone should have at least one, configurable, hard button. The specific configurations would be user-settable by app context, but a good starting set of defaults would include:

Camera: shutter button.
Stopwatch: start/stop button (soft buttons are particularly ill-suited for this application)
Reader, browser: Page Down[1]
Home screen: this will vary, but for me it would be to bring up the dialer.
Phone conversation: Mute toggle

 Of course, this button should be placed where it is very easy to activate while holding the phone one-handed. 
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[1] Of course an even better implementation for PageUp/PageDown would be the volume rocker, but that is out of scope for a single button. PageDown would be at least 75% better.