Two and a half years on from the release of the two mainstream VR headsets, the Oculus Rift and HTC Vive, both have come down in price significantly, but VR remains an expensive game to get into, especially if you want to stay on the cutting edge. While both headset options can now be had for under $500 for the complete package, there are options to make it more of a premium experience and the HTC Vive wireless module is one of them.
At $300 it's far from cheap, but it converts the existing mid-range VR headset into one that can operate entirely without wires. It's a relatively chunky, winged accessory that hooks on to the back of the headset, but it adds wireless connectivity and a built-in battery for two and a half hours of VR gaming while entirely untethered. That does mean a cable dangles down your back to the battery pack itself, but you're still not tied to anything that isn't attached to you.
All of it connects up to a PCIe card which acts as a wireless adaptor for the headset accessory. That does mean you'll still need to be within six metres of your PC at all times, but PCIe riser cables might be able to extend that range.
If you happen to own the even more expensive Vive Pro headset, which offers greater resolution, ergonomics, and built-in audio than the standard Vive, you can also upgrade it to operate wirelessly, but there is a catch -- it's even more expensive.
Oddly enough, considering it was announced at a similar time to the Vive wireless module, the Vive Pro needs an additional adaptor to make the new wireless module fit. That adaptor costs an additional $60, so all in, the wireless Vive Pro experience is even more expensive, but considering you're spending upwards of $1,500 already, that additional expense isn't a massive extra.