So!
I never heard of merge, but it looks very nice. Kind’a like daydream, i assume?
The phone you are using is important. if it supports WebVR you can use the WebVR experience helper, but if it doesn’t (like in the case of iOS), it will fall back the device orientation camera, which is a bit limited due to lack of API support. But! it is still working 
I don’t know how the touch registers on the device itself. The GearVR, for example, registered itself as a “controller”, so you can use the controller API. Daydream as well has an external controller. If MergeVR registers the touch as regular touch events, you can use the Pointer API we have integrated in babylon. If it registers as a gamepad, you can use our Gamepad API. Is there any documentation or API definition for the device itself? Maybe I will be able to help there.
BTW, you can always use the Gaze support we have in the experience helper, to use the direction you are looking at as a pointer. You can read about it here - Use the WebVR experience helper - Babylon.js Documentation
If you have some more information about the device itself, I might be able to help further.