Following up on Reddit posts highlighting some initial testing in Japan, we can confirm that PlayStation VR does indeed work as a personal viewer for PC, Mac, Wii U and Xbox One - indeed any HDMI source should work just fine.
We tested this by setting up PSVR as normal, attaching the headset to the external processor and plugging that into the mains. The HDMI input on the rear of the box accepts a video signal from any HDMI source and PlayStation VR acts exactly like as it would when handling non-VR content from a standard PS4. However, the one major drawback is that the processor box must be connected to the PS4 via USB, it requires the Sony-specific handshake, and you can't just plug it into another system. In short, if you want to use PSVR with another HDMI system, you're still going to need a PS4 close to hand - though the PS Camera does not need to be attached.
The processor box pipes through the HDMI output as standard to your HDTV via the social screen output, while the view inside the headset blows up the HDMI feed to a cinema-size display right in front of your eyes. Head-tracking still works to a certain extent - you can adjust your view of the 'cinema screen' by looking around as per normal. This would appear to be handled by the processor box and the headset's sensors.
In terms of the quality of the presentation, there's little doubt that you're getting a phenomenal sense of scale here - and PSVR's excellent handling of the screen-door effect means that the image is soft, rather than pixelated or grainy. However, we're still looking at a significantly reduced resolution overall, so the effect isn't exactly brilliant.
It's a 'nice' bonus feature to have, as opposed to a genuine alternative to using an HDTV, and this applies whether you're using PS4 or any other HDMI source. It's also worth pointing out that 3D sources are processed in stereo - which would have been a nice bonus feature.
The next logical question would be whether PlayStation VR can be used as a full VR solution for PC gaming. Well, the interfaces used by the hardware are standard - USB 3.0 and a HDMI 1.4 signal that outputs 1920x1080 at either 90Hz or 120Hz. So in theory, it's definitely possible, but it would require a great deal of reverse engineering.
For starters, the USB protocols would need to be intercepted and reversed (we imagine that off-the-shelf controllers are used, which should make life easier) while the tracking solution would need to be rewritten from scratch to accommodate PSVR's unique RGB lighting set-up, for headset, Dual Shock 4 and PS Move support.
And even then, the task would not be complete - the entire project would need to be integrated into an existing VR framework in order to make existing PC titles work with the hardware. Let's just say that the task would not be trivial.
As things stand, PSVR compatibility with other systems - such as it is - is a happy accident of the system utilising an existing standard. As far as we're aware, HDMI transmitters can question the receiver to check that the right device is attached (which is why you can't attach another VR headset to the PSVR's external processor) but there's no easy way for the processing box to lock out non-approved sources.
So with that in mind, PSVR treats any standard HDMI input exactly as it would if it were coming from the PlayStation 4. It's a neat trick, but it's safe to say that the use-case scenarios are highly limited and of course, it should go without saying that PSVR should only be purchased primarily for use with PlayStation 4 hardware.