On a BlackBerry, when it is put in the charger, it goes into Bedside Mode, and the clock application is shown. The user can set up the profile to be used during this state (i.e. what notifications to allow, etc.). It can also be programmed to only enter bedside mode during certain hours.
I know it's not exactly what you're asking for, but it's something they've done for several years, and done quite well. I'm hoping they extend it, and keep it in BlackBerry 10.
For me the nicest variant of this idea was the TouchStone thign from Palm/HP/Web OS.
Inductive charger that triggered a configurable mode on your phone -> Drop the phone on a magnet, get a clock or whatever and the phone charges without searching the plug beneath the bed.
Just to clarify, BlackBerry does this sans a dock. It simply activates whenever being charged, whatever the source. However, it can and does distinguish between USB and dock. Just unsure if it actually uses it in the software, because I always use a dock nowadays.
I know it's not exactly what you're asking for, but it's something they've done for several years, and done quite well. I'm hoping they extend it, and keep it in BlackBerry 10.