Hollywood has basically been doing what Kohlson has described for decades.
The common device historically used for this synchronization is called a clapboard. Here are some
Google Image Search results that help illustrate this device.
Using this device serves several functions. It provides a visual indicator of the synchronization point (when the clapper and the board meet together). It also provides an audio cue, noticeable on an audio soundtrack display as a large waveform. Modern clapboards often feature an electronic tone which is even easier to spot. It also identifies the particular clip, helpful if you have multiple takes or shots on the same recording medium (like a spool of film or a digital memory card).
In the old days of film-based cinematography, the film camera probably didn't have its own audio recording system. The audio was recorded on a different device. For instance, while the motion picture imagery might have been filmed on an ARRI motion picture camera, the audio might have been captured on a Nagra recorder.
Devices like the clipboard have enabled synchronization.
This technique is still valid. Even if you have an adequate camcorder for the videography, maybe the audio recording circuitry and microphone aren't up to snuff, so you decide to use an external audio recorder like a Zoom.
There are even iPad/iPhone based clapboard apps that replace the physical clapboard.