I have the
DOT, and until the DOT works, it does not have me
It is probably an ambient light sensor as others have said (since I have NO special options and the basic radio, no Nav, no bugger all).... my speculation is that it might be a small LED to warn you if your alarm went off whilst you were away (e.g strong wind etc. or an actual attempt to break-in)... Need to test this by sitting in the car and turning alarm on
Couple of things I found on this forum which are useful and not documented AFIAK:-
Charger socket under the dashboard on passenger side: feel under the dash near the back of footwell nearer to the centre of car (opposite side to steering wheel). Useful for a USB charger cable that you can keep out the way in the net in the footwell, rather than clogging up you cup tray... or a permanent cable for 'phone or portable Satnav.
Scroll wheel on steering wheel for recent calls: Press TEL twice, and turn scroll wheel for list of names/number you have called on dashboard instrument mini-screen (This of course works for changing radio stations and songs as well, which is documented).