FWIW, I've seen several references in a few threads to maintaining sync and assuring clocking accuracy - I assume this implies tracking other than digital audio and/or video, or needing accuracy over a long period with no option or desire for manual resync in post.

This might not be applicable to your situation, but I've run over 3 hours of HDV tapes with nearly continuous audio going to a laptop with no sync. I then manually aligned the laptop audio to the camera audio dead on to a frame for various segments of that 3 hours of audio and capture video (would prefer sample accurate, but it is video :-). It was a live shoot where slating wouldn't have been possible for most of the shots. Granted I'm only aligning in 1-2 minute segments in post for a 15 minute video, which is a little different than tracking a full hour or two needing guaranteed longterm sync in post. But in this case, there was no drift during any segment of audio. This is just a testament of stable clocking and the fact that transferring digital maintains frame-accuracy since there is no reclocking more than anything else. I can't speak for other digital formats, but at least our Sony FX1 and RME Fireface seem to be quite accurate (I know the RME clock is very accurate), but I wouldn't expect more than a sample or two difference with more recent clocking circuits. Most, even on a consumer level, have significantly improved over the past 5 years to the point that running free is more accurate than running SMPTE to analog tape was years ago (at least for audio, which is my main background).

As Bob suggested, slate should do fine in most cases, but with more detail on what you need to do there might be other suggestions.