Would milk be considered cholov yisroel if someone was watching via webcam?
From these sources you can see that a webcam would at least be enough to create a situation of fear (looking over the shoulder) on the part of the gentile regarding anything that is within view of the camera(s).
Would this be enough that when the Jew is watching via the webcam we would consider the milking to having been witnessed by the Jew is the next step in the sh'eilah.
What is the definition of "re'eeyah" with regard to חלב ישראל is an issue that was taken up by far greater people than us on mi.yodeya!
In Yalkut Yoesf Yoreh Deah 81:9 seems relevant:
גוי החולב חלב מעדר שיש שם רק בהמות טהורות, אף שאין בעדר בהמה טמאה, יש לאסור את החלב כל שאין הישראל רואהו, או שאינו נכנס ויוצא באמצע החליבה. ואם הישראל יושב בחוץ לשמור על הגוי החולב שלא יביא חלב טמא ממקום אחר, מותר, ובלבד שיראה את כלי החליבה לפני החליבה שיהיו נקיים.
A non-jew who milks animals in a herd that only has tahor animals, the milk is assur unless a Jew watched, or was at least yotzae v'nichnas. If a Jew was sat outside to make sure that no tamei animals (or tamei milk) were brought from somewhere else, the milk is mutar on condition that the Jew checked the kelim (that would receive the milk) to be sure they were clean (and empty) before milking started.
My guess is that according to him, a camera wouldn't be sufficient, because it can't check the inside of the milking kelim (and generally because there are other blind spots not covered by cameras).
From an answer to your question earlier:
Chalav Yisrael requires that a Jew watch the milking (though he can step in and out every few minutes); R' Moshe Feinstein feels that "knowing for sure" is as good as watching, so I think he'd allow a video camera. I don't know if other rabbis require actual watching, or if video would count too.
I strongly suspect it would be up to individual hechsherim at that point. It wouldn't surprise me if those who accept R' Moshe's premise as the base halacha would allow the cameras to satisfy the chumra of having a mashgiach watching. For those who require literal Jewish eyeballs watching as the basic halacha, I'm not sure.
UPDATE: Thanks Isaac! In the shiur linked below, a rabbi from the OU said that some Israeli hechsherim will allow video-cameras for chalav yisrael; none of the American hechsherim do though. My impression is that if the OU will mark something "chalav yisrael", they'll keep the standards of other American chalav yisrael hechshers (e.g. requiring a Jew to pour in the cultures, not just the rennet), so I doubt the OU would mark something video-camera'd as "chalavy yisrael."