This thing looks like a clone of the
Samsung Gear VR headset. The big difference to devices like the Oculus Rift is that it uses a smartphone for both the display and processing, instead of being connected to a PC and using a built-in display (or displays). The flipside is of course that you're not tethered to anything, so you could at least theorethically move around freely. One defining factor will be software support. Oculus have a lot of developer support by virtue of being first out the gate, the HTC Vive is backed by Valve, and Sony's Morpheus is at least theorethically backed by the Playstation development community. Unless some kind of standard software interfaces are worked out, that won't leave much space for the smaller players. Google developed an SDK for their Cardboard headset which I guess will be the standard API for Android, but I have no idea about other platforms.
The castAR is different, (so far) it only does augmented reality, and works by projecting onto a reflective surface.