Whatever happened to Google's "Project Soli", which did this with millimeter radar? Dev kits are supposed to be available in Fall 2016, so this should be out Real Soon Now.
As I read it, that technology doesn't provide haptic feedback, it just tracks gestures.
Agreed. But in combination with this, you could have the best of both worlds - I suspect Soli would read a much finer level of detail than anything ultra sound would, but this should give the haptic feedback that Soli lacked.