This needs a patent
Because nobody ever thought of an infrared sensor before. You could even use it in alarms...........
Apple hopes to patent a gizmo that uses heat and infrared light to know when you're nearby. The US Patent and Trademark Office (USPTO) has published an application, titled Infrared Sensors for Electronic Devices, drawn up the company that describes technology which would use infrared to detect the presence of something and …
Like most patents, the submitter is trying to demonstrate a way of using already available 'stuff' in a way that might be different from other people.
The decision that will probably reside in the long term with the courts is, 'Is this method sufficiently different from other similar methods already patented by other companies'.
Now what would be true innovation would be if the device alerted the used of the presence of someone using a rival makers phone. (Then sent out a taser/lightning bolt to disable the other use/enemy... Just dreaming because the storms last night didn't let me get much sleep) :)
Note that I have not sided on Apple or Samsung/Android here. Samsung/Google could equally apply for that patent. Google may have already done so already... IMHO,it is not beyond the stupidity of the USPTO to grant almost identical patents to rival companies.