Modifying sensitivity of Google Nexus S power button? I keep accidentally turning the phone off/on by pressing the power button when I pick up the phone or take it out of its holster.

I would like to make the power button require a longer hold before it performs its action. Obviously this would require a different gesture to then perform a full shutdown.

Is there a mod or app that anyone is aware of that can help with this? When I'm using the device during a sporting activity for example, I can't really afford to have to unlock the screen, because even without a screen lock, sliding the unlock slider is often not possible.

I find it incredible with this form factor how easy it is to accidentally shut down the screen, and then you can't just turn it back on without having to perform some additional gesture on the screen.
The only thing you can do is to maybe put a "gel case" on the device. That should make it less sensitive to presses. 

The only other option would to modify the source code of the android core.