Command-line tool to split video at timepoints?
ffmpeg is the obvious choice. 

ffmpeg -i x.mov -ss 00:05:00 -t 00:01:00 y.mov


will split out a segment of the movie 1 minute long from minute 5.

I've not had much luck with lip-sync when doing this. I think there a problems with both decoding and re-encoding the GOP structure and the equivalent AAC or MPEG1 audio structures; but the underlying issue must be that the audio and video frame rates are not linked, e.g. 48 kHz for the audio and 29.97 fps.