Google cardboard is a neat concept. It is cheap, easy to setup and allows anyone with a phone and a heartbeat to try VR. Google has greatly increased the apps available for this format in their Google Play store, therefore just like any other open platform other devices will come along that take advantage of this. Which of course is a good thing.
One such device is the Go4D C1-Glass from Goggle Tech. It deliverers a very similar experience to Google Cardboard with the advantage of being able to place the device in your pocket just like glasses. How important this is to you depends on your "geek level"? Are you OK with watching a movie or playing a VR game on the train? If so, then this product may be for you as its far more convenient than Google Cardboard. The main downside of the Go4D C1 is light leakage from the outside since this does not have any form of blockage. However in the case of my phone it worked perfectly well in a regularly lit room.
The Field of view (FOV) with the Go4D is dependent on your screen size. I tried it on my largest smart phone the Droid Turbo at 5.2 inches with a resolution of 2560 x 1440 which equates to 565 ppi. While the Oculus offers a 110-degree field of view – the largest of any VR device Google Cardboard offers about 90 degrees and this devices seems similar to Cardboard.
Go4D will work with any Google Cardboard app however they also provide a few apps of their own such as Go4D world which allows you to browse movies, games and various apps.
The Go4D 2.2D Player Pro (mouthful) lets you watch a movie either stored locally on your phone or streamed from the internet or your local network. It works well for any movie so long as the audio is not encoded in DD5.1 or DTS, you'll need to convert those file formats first.
Compatibility with the latest smartphones:
C1-Glass is compatible with most smartphones with a screen size from 4 inches to 6 inches, including the Google Nexus 5, Nexus 6, and Motorola Moto X, iPhone 5, iPhone 6, iPhone 6+, LG Optimus G3 and LG Optimus G3a, Samsung Galaxy S4, Galaxy S5, Galaxy S6, Note 3, Note 4, Sony Xperia A, Sony Xperia Z, HTC One, Xiaomi Mi3, Sharp Aquos Zeta SH-01F, Huawei Honor 3C, and many more.
Goggletech Go4D C1-Glass can be ordered directly from their site for $22 plus shipping