Thanks for your reply, Jim.
I just thought it was quite unusual that none of the cars I checked in dealers' inventories had this option. Online I have looked at 25+ "loaded" vehicles at Southern California dealers, and not one shows this option.
This is surprising, in that just about every moderately equipped vehicle I have seen (Toyota Rav4, Acura, Volvo, etc.,) has this feature.
I'm wondering if Lexus has found some problems with this option, and is not shipping it yet.