When looking for a third party camera application, often users look no further than the Google Camera. Its HDR+ processing algorithms can upgrade any camera sensor, and as such ports of the Google Camera to other devices are sought after by the community at large. That's not to say it's perfect though. It still has its own share of missing features, one of which is a feature currently only available in Google Camera 6.1, which is only (officially) available on the Google Pixel 3 as of the time of writing. Google Camera 6.1 supports external microphones during video recording, so you can use your headset's built-in microphone for audio.
If you'd like to use an external microphone on your Google Pixel or Google Pixel 2, you can do that as well simply by installing the latest APK. The latest version of the app has RAW support, but it also has a brand new user interface as well. The APK will install on previous Pixel phones. Newer features from the Google Pixel 3 don't show up in the latest version of the app, so don't expect to have features like Top Shot and Night Sight just by updating.
The external microphone only appears to work with headsets that feature a built-in microphone, so something such as the Google Pixel Buds would be perfect for the job. The usage of an external headset microphone allows you to do better voice-overs, especially in loud, crowded areas where you aren't going to be forced to move the phone itself closer to your mouth to be heard. Most of the time though, you'll want to be using your phone's microphone as it will likely be better quality than what your headset can produce. You can check out our article to download the latest version of the Google Camera application below.
Thanks XDA Senior Member cstark27 for the tip!