Add sound feedback at boot
There are two cases where extra sound feedback would be useful.
The first one is when the button is being pressed. There is the light, but when the phone is on the charger, the color change feels somewhat unclear: "is it the phone turning on or a change of charging status?". Making the motor run would suggest that the phone is more "alive" now, that is, the button press was accepted.
The second case is related to the boot password entry. It's necessary every time the phone is rebooted, meaning when rebooting while hacking on the OS, or when rebooting to do updates. Shutdown is not instant, therefore I usually put the phone aside, and I find that I often forget about it (especially when using the reinstall+reboot script). Some audio feedback would be very useful there.