Some people own a night vision camera, one just for fun, like outdoor enthusiast who sets up wildlife cameras in the woods. Again, that's a specialized piece of equipment that doesn't work with the video enthusiast's standard gear.
There are dozens of "night vision" apps for smartphones and mobile devices. These apps utilize visual effects to make video shot through the devices camera appear to be night vision, but it's not a true night vision camera. It's a green tint applied to the video with some adjustments made to the image's contrast. A recent Kickstarter campaign has launched a true night vision camera for smartphones and mobile devices. The Snooperscope is a small wireless infrared night vision camera that interfaces with a mobile device.
Using a magnetic mount, the Snooperscope mounts to a mobile device. It isn't a clip-on lens, the Snooperscope is its own camera, that streams through Wi-Fi to the mobile device. This is much like the Sony QX100. The Snooperscope doesn't have to be mounted to a mobile device however, it has standard threads for mounting to a tripod or other camera mount. Its small size makes it ideal for portable applications. The onboard battery powers the Snooperscope so it doesn't drain resources from the linked mobile device. Again, this is a product that was supported through a Kickstarter campaign. It it not yet available on the market but it has received full funding so will likely be available in the near future. The estimated price for the Snooperscope is approximately $100.