News HTC teases mobile virtual reality plans

With the limitation that:

Then there are two choices:
1) Put the phone in a headset, with the phone screen used as the VR display
2) Link the phone to a headset with a cable, with the HMD having its own screen(s).

2 being the more expensive option, it only makes sense if your phone lacks a screen suitable for VR in the first place. 2 can also end up with turds like the LG 360 as manufacturers cut corners to keep the cost down.