Can this tractor beam approach be used to gently push a finger in mid-air? Or create the illusion of a solid object where there's none? I'm wondering about applications to virtual reality.
Also, what if the tractor beam inadvertently attaches to your eardrum? (Ok, headphones could solve that)
(Hmm sounds like something that might get patented. Can this be prior art and I donate to you guys?)
Or spread multiple transmitters around the room (or even attached to the person's suit) to (try to) prevent blockage. That could work but there are loopholes and thus it's both expensive and not theoretically satisfying.