The question that always goes through my mind whenever I see something like this--and the articles don't make any mention of it--is, "Can it be calibrated?"
I've run across an app or two where I remember reading that they included the ability to be calibrated (one being the Lepsi device mentioned not too long ago), and the TG program over on the Watchmaking forum includes a calibration function. What about all the other ones out there? (I haven't tried any of them out, so maybe someone else can provide some insight into this).
Consumer audio hardware is not necessarily that accurate, and an error of around 50 ppm (somewhat typical, most usually sit under 100ppm) is already an error of some 4 seconds/day. Sure, the program may think that it's receiving audio data at 44.1 khz (picking a rate for an example), but is the ADC actually sampling the audio at 44.1 khz or is it off by a few parts per million?