OnePlus Loop VR
Android smartphone manufacturer OnePlus has a similar headset to the Gear VR in the shape of the Loop VR. It looks similar but is capable of working with "most handsets between 5 and 6-inches" and differs from Samsung's model because it doesn't have any onboard hardware.
You slot the smartphone in the front of the device, which is padded and comes with a head strap for comfort, and in many ways it works like a posh version of Google Cardboard, except it has no button, so it's not completely Cardboard compatible.
What's significantly different about the OnePlus Loop VR is that it is free, or was free. OnePlus made 30,000 headsets and they were available on a first come first served basis, but sold out almost straight away. The only cost was the price of shipping.
As a piece of technology, there's not too much to the Loop VR. It has orthoscopic lenses and 100-degree field of view, but the experience - including motion sensing - is all done by your phone. Naturally, the better the phone the better the experience. The manufacturer would clearly like that to be the OnePlus 3 when it is available, as this headset is pitched as the partner for the virtual launch of OnePlus' next handset.
LG 360 VR
The LG 360 VR is a headset that you have to connect to your LG G5 via the USB Type-C cable, rather than slipping your phone into the front as you do with Cardboard. It takes the form of a pair of glasses, which you wear rather more conventionally than others. It's better than Cardboard and other basic systems because you don't have to hold it to your face all the time.
The headset itself has two 1.8-inch IPS displays inside, one for each eye, each with a resolution of 960 x 720 pixels, resulting in 639ppi. Those displays sit behind lenses that can be independently focused (you can't wear glasses and 360 VR at the same time), as well as being able to adjust the width to get the best fit to your face and ensure stereoscopic vision.
The headset also carries the controls for your VR environment, with an ok and back button for basic click navigation. Otherwise, it has motion sensors, to allow you to look around the virtual world you're in. There's also a sensor between your eyes. This detects when the headset is being worn.
When it comes to audio, there's a 3.5mm headphone socket on the underside of the 360 VR headset. If you don't use this, the sound comes out of your smartphone, which may be some distance away, or perhaps in your pocket. The LG 360 VR is available from some retailers, priced at £200.
Google Cardboard was first unveiled in 2014, as quite literally a folding cardboard container into which a smartphone could be placed. The beauty of Google Cardboard is two-fold: firstly, the hardware cost is almost minimal, often free, and secondly, it's universal, supporting a wide range of smartphone models - essentially, anything that will fit into the front and stay secure.
Google Cardboard is something of a breakaway success, allowing people to sample VR content (be that from Google or elsewhere), without having to invest in a more substantial system: Google reports that five million Cardboard viewers have shipped. Google has a range of applications for the device, and has highlighted VR for development and investment in the future. Importantly, Cardboard is not only this cardboard viewer, but also the name of the VR platform from Google.
Cardboard is really an ad hoc VR viewer: there's no head strap and if there was it would be uncomfortable to wear, instead intended to be held to the face to view the content. There are a range of Cardboard apps for content, as well as being able to view 360 environments such as Google Street View or watching 360 content on YouTube. Cardboard makes perfect sense: if you want to dip your toe into VR, this is a good place to start.
Related to Google Cardboard is Daydream, the next-generation of VR from Google. Where Cardboard was about accessibility and laying the foundations for VR content via your smartphone, Daydream is the future for Google and Android virtual reality.
Daydream was announced at Google I/O and will be arriving later in 2016, with Google saying that Daydream was to be an integrated part of Android N - the next version of Google's mobile operating system.
Daydream will make some fundamental changes to the Android VR world, outlining a minimum spec for Daydream devices and producing a reference design for the hardware, introducing, for the first time, a spec for a separate controller.
We've seen previews of a lobby system to make it easier to navigate around VR content and it's been promised that a whole range of Daydream certified devices and accessories will launch later in the year.
Zeiss VR One and One GX
Optics specialist Zeiss has its own virtual reality headset that converts an iPhone or Android device into an immersive 3D experience. The Zeiss VROne is very similar to Samsung's Gear VR headset, but with a universal design. The VR One features a tray to hold your phone and you'll need the appropriate tray for your handset, be that iPhone 6, SGS6, SonyXperia Z5 and so on.
The VR One will work with any app that is made for VR headsets such as Cardboard apps, delivering two images, so that each eye is separate and allows for a 3D experience. The VR One has a head strap and the One GX, like Cardboard, is designed for holding to your face. The Zeiss VR One is available now for about £110.
There are many more systems like the Zeiss VR that will accept phones in various forms and offer a similar approach to VR. If you're getting into smartphone-based VR, this is a good way to go.