[NOT MY PROJECT actually, but possibly interesting for all those Oculus fans out there.]
Basic idea: Use a headset with two plastic lenses, slide your Android smartphone in so you have a display, play immersively.
Heise (German, generally-competent IT magazine) says that lag tends to be better than with the Oculus, and that the immersion works anyway.
Review (German unfortunately): http://www.heise.de/newsticker/meldung/Dive-Die-Virtual-Reality-Brille-mit-dem-Smartphone-1854860.html
The low lag isn’t really a surprise, the motion sensors are inside the phone and don’t need to use any communication protocols to submit their data to the CPU.
What did surprise me that the immersion works despite a rather small field of vision.