Now with the final releases, it comes with more stable and easy to use.
Smart Controller 3 its the most light and easy to use for controlling the vMix Software. And its better than the previous app (version 1 and 2)

8 buttons for Camera Selection, Cut, Auto and Transition 1.
Just connect your Smartphone on the same network with vMix , and you good to go. It works with vMix from Version 20 to the Latest version.

You can try before you buy (4 Channel limited) here:
https://play.google.com/store/apps/details?id=com.vicksmedia.smartcontrolindo