[PPCFreak]

I have not heard or seen software for this either.....and not sure if the vib motor would last long enough to do this.

The vib motors are not known to be very long lasting if you use then for long durations.
And sometimes long vib durations can lead to the motor shifting and / or loosing contact with the power pins on the main board.

Still would be an intersting software to play around with.