I don't think it's just the patents on the arrows involved, there's also considerable "location" technology (and additional patents) behind the arrows.
Depending on your interest, you can take a look a the V1 patents filed by Valentine Research:
6175324 5250951 5116248 4878061
5917441 5206651 5083129 4631542
5900832 5164729 5068663 D338841
5856801 5151701 5020754
5852417 5146226 4994775
5300932 5125110 4973925
and plug the patent number into this link, for detailed information. D338841 is the one for the housing unit.
http://patft1.uspto.gov/netahtml/PTO/srchnum.htm
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