Sounds

The pointer solution is a great way to, more or less, force the user to look in a certain way. Using a pointer is obvious to the user, so he is more inclined to follow the directions you give, but if you just want to make the user aware of the presence of an item in the space around him, you can consider using subtle spatial sounds.

Imagine that you are designing a game where the user has the option to pick up items from the scene around him. It would be helpful to have those items make subtle sounds. Since the spatial sound system of the HoloLens is extremely accurate, we can precisely place the origin of the sound at the location where the objects are, and the user will be able to find things this way. We, as people, are hardwired to find sources of audio by constantly slightly moving our heads to find where the sounds are coming from. The moment we hear something behind us, we will turn around to see what it is. We can use this to our advantage.

Having an item making sounds will draw the user toward it and help them find the object. Of course, this won't work anymore when we have dozens of objects, all happily chirping and bleeping away. The user will drown in the sounds and will not be able to identify the source anymore. However, when used in moderation, this can be extremely powerful and make the sense of realism even greater.