Basics

A Cheap(ish) way of SORT OF? (insert definition snobbery here) doing VR and to an EVEN LESSER capability AR and MR
Uses a Smartphone and a headset with lenses and a head mount system to make a rudimentary All in One HMD
Granted due to the display not being an optimized geometry quality is lesser, also depending on headset quality lenses may be bad (see the headset reccomendations section below)
Also uses only Accelorometer-Compass-Gyroscope Dead Reconing for tracking and thus suffers from drifting in tracking overtime
- ALSO this limits the system to 3DOF unless an add-on like NOLO VR or PSVR Emulation is used
It can be a HMD PC Tethering setup with the correct software, but most Smartphone IO is insufficient for high speed data transfer
Also screen resolution is reduced when magnified and stretched etc by the lenses so ever 1440p looks more like 720p or a bit less
Issues like the Screen Door Effect also arise due to the screen issue
Overheating may be an issue due to most programs essentially maxing out the smartphone's hardware, but propper passive and/or active cooling aleviate this

Main Use Cases

There is some debate as to if a low quality experience will "scare off" non-early adopters, but it is a VERY cheap place to start if one has a good smartphone already and 10-60 USD to burn

CLip on Model goes for ~15 USD, but can be folded and put in a pocket/large wallet/bag
One of these is better than nothing due to transportation constraints