And like a coincidence, Viofo were the first. Maybe they were just lucky and Novatek implemented this options on their first A119. The audio warning is from the first 96xxx but is not available today in all dashcams and this is good for the companies which are smart and are using this great feature.
I requested audible notifications in 2014 (there were Korean cameras doing spoken warnings back then) but even beeps was a step up from no sound at all, it wasn't possible on the earlier chipset but was told we could have it on the upcoming chipset, when we started on the SG9663DC in 2015 it was available, was a quite while before we released and could actually take advantage of the function as there were other things that needed sorting to get the product stable before release, lead times are like that though so part of the process we have to go through, you're right that there are many that don't implement this function today even though it is available to all, some brands just don't get it I guess, their loss
I didn't knew about audio warning on korean dashcam even I had two korean brands 6-7 years ago and reading this forum daily.
there were more than 300 Korean brands doing dashcams back then, majority never sold outside of the Korean domestic market so really only maybe 4 or 5 brands that were exporting at that time, not a lot more than that still do business outside of Korea, they're way past the saturation point in their home market so I suspect quite a lot of the smaller players there that never found an export partner no longer exist