[itishappy]

In theory, but probably not in practice. The fancy non-metal-detector airport security scanners use mmWave to detect object through clothing, so the light itself capable of producing high-resolution images. However, cheap home automation sensors are probably not imaging, so you're probably going to be stuck with a single depth measurement.

[jcrawfordor]

HomeSeer manufactures a Z-Wave millimeter wave radar sensor that uses imaging techniques to detect motion in specified zones, and they intend to release pet differentiation as a firmware update. I'm seeing enough negative reviews of how it works in practice that I haven't dropped the money on one, but I'm hoping that the technology will improve quickly. It's only $59 too, which isn't much more than PIR Z-Wave sensors. Maybe I will buy one to try out...