To sign up go to:
Stagelight Beta Request Form
This version will be for the version number two and can be accessed for many devices in difference to the first.
Just for 7 inch and up though and here is what is demanded of the devices:
Minimum device specs are:
* Dual-Core CPU
* 1024 x 768 resolution screen
* 1GB RAM (512mb free)
* 300MB of free space
* Android 4.4+
Recommended device specs are:
* Quad-Core CPU
* 2GB RAM or more
This application looks like it can be an interesting thing and here is the official video to see what to be expected.