I don't have a garage, but I think this would be a useful feature if I did

I've had this idea for a while, too. But I'd even prefer them to fold just when within an even closer range of the garage. Namely, have the Homelink activate at many feet away, but the mirrors fold within a few.

But then what happens when the car's GPS receiver glitches precisely at the moment when your folded mirrors are just clearing your garage door opening? Smash! Probably would be wiser to deploy the mirrors when shifting into Drive rather than based on a location trigger.

Has this feature not already been added?  I currently do not have homelink on my SR+ (it's on order), buy my mirrors do fold when I approach my garage.  I think it's called location mirror activation or something similar to that.