To enable the Simultaneous Interaction feature, you have to add below content to your AndroidManifest.xml.
<uses-feature android:name="wave.feature.simultaneous_interaction" android:required="true" />
Or you can enable the Simultaneous Interaction feature from the menu item Wave > Interaction Mode > Enable Simultaneous Interaction as mentioned in Raycast.
After imported the Essence sample (refer to Samples), you will see a Raycast sample which demonstrates features Gaze, Controller and Hand concurrently at Assets > Samples > Wave > Essence > Essence > Raycast.
And another RaycastEyeTracking sample demonstrates features Eye Gaze (see Eye Tracking), Controller and Hand concurrently.