It turns out the HoloLens Companion app (opens in new tab) lets you broadcast what you're seeing via the headset to your Windows 10 PC or Windows 10 Mobile device. It basically means others can watch a live stream of whatever you're seeing through the headset, making it a more social experience.
The app, which connects to the HoloLens via Wi-Fi, will also let you control the headset remotely, with the ability to launch and kill apps on the headset via PC and mobile.
It doesn't stop there: You can remotely use your phone or PC to take photos or videos with HoloLens, and view and download them via the app as well. Your PC or mobile's keyboard will also be able to input directly to the headset.
Of course, the Developer Edition of the HoloLens costs $3,000 (about £2,160/AU$4,202), so the Companion app won't be useful to you just yet unless you're a dev or have the cash to drop.
Still, if you have a Windows 10 PC or phone, it's worth checking out to see just what kind of features you'll have to play around with once a more affordable, consumer-ready headset goes on sale.