I don't know how to do this or if it's even possible right now. If there's a way, that'd be fantastic! If not then... not so fantastic.
For example, if I want to be able to test if a player is looking at a cube to change it's color, like you're highlighting it.
Or another example, if I want the player to be able to press a button in game by pressing "E" on their keyboard while looking at it.