The empty button is a remnant of the Euro Spec and I think was used for getting video signals.
The SVC button is a feature of only the 2003 model W220. You have an AUX Input on the left side of your glove box for ipods/zunes/8-tracks.
Video is a complicated yes...
You can certainly find ways to do it, the issue is that it's not DOT approved and is disabled by default in the USA.
That might not be the case where you are. Do a search for video. I've found people who have done it before.
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