What's needed for automatic low beam lights?

[jac]

Hi,

I have always wanted automatic low beams... you know... those that come on by themselves when it is dark. I have 2001 3.0i X5 which does not have this feature, but I have seen it in others (perhaps later models or maybe models with NAV?) Anyway... anyone know what parts would be needed to retrofit that into a 2001 3.0i X5?

I know the switch on the dash will need to be replaced, but I am certain there has to be a light detector somewhere which I imagine is not part of my X currently... Is the light detector perhaps embedded in the more advanced rearview mirrors (those with compass)?

Thanks.