Virtual Reality. It still has a way to go, but the technology is incredible and immersive when done well.

The barriers at the moment are a mix of technical (high computing power, tethered systems, ongoing needs to improve camera and component sizes and weights to improve headset comfort) and conent (there is content but it is growing slowly; gaming and other entertainment seem the most likely uses for the tech, or ‘spatial computing’ if Apple can broaden the use scenarios).

I think the big shifts will come in the next few years:

• Improved components and production lines - Apples extremely expensive headset makes more sense when you see it as the vanguard of a new production line - economies of scale, and ongoing technical improvements should bring even their current headset down in price in a few years. The iPhone did well initially but it really took off a few years in as Apple optimised it’s production lines and costs, pumping up quality while maintaining price (although it was premium even then)
• Streaming tech - both local wifi etc streaming from a PC to free up the user from tethering, and also longer term the potential for cloud based computing streaming to headsets. There will be technical issues but having used Stadia I’m convinced they can be overcome; although it failed commerically that (and other streaming techs) show low latency streaming for gaming can be done. Although with so much more to track and keep in sync VR will be harder; but streaming content will unleash VRs potential to mass market.
• Procedural and “AI” generated VR content - I think content generation will benefit massively from the increased procedural and so-called AI generated technology. This will benefit gaming (and other entertainment) in general but that will feed into VR.