How could one automatically sync two audio recordings?

Let's say I want to do a video presentation, where I want to record the audio that I want to use, onto a separate device, separated from the video camera.

I have now tested Allison Deal's Video sync (also linked under "Update II" in the question) and it seems to do the job.

In the root of its git directory there is a file called "alignment_by_row_channels.py". If you comment out the test code at the end of that file, it can take two mp4 videos and print the time offset between the audio in the two videos.

I tested it with a Canon HF200 video camera and an LG G2 android phone, with talk and finger snaps and very low volume on the video camera. I then manually analyzed the sound tracks with audacity.

The alignment_by_row_channels.py script indicated an offset between the two track of 15.1893 seconds. My manual analysis by looking at waveforms gave 15.181 seconds (audacity does not output less than millisecond resolution, at least not by default).

The difference is only 8.3 milliseconds or thereabouts which seems to indicate that "alignment_by_row_channels.py" does the job.

(Beware that the git repo is hefty, probably due to deleted big objects)

One way of doing that is to record the audio also with the camera, and then use your eyes and ears to sync the audio up using Audacity. How do that is described here:

How to Sync Video and Separately Recorded Audio, Using Only Open-Source Software

Update: I have found this python application with matching Android clapboard that could do the trick. It seems to work by syncing to a special sound recorded both in the video file and in the external audio file.

Update II: And here is another one in python, that is meant to be used to sync up Yotube videos recorded at the same concert.