I believe you can access it via the Youtube API, for example you should be able to access the most recent upload a user has done by:
http://gdata.youtube.com/feeds/api/users/[USER-ID]/uploads?max-results=1
so for example
http://gdata.youtube.com/feeds/api/users/askhodgetwins/uploads?max-results=1
retrieves the most recent upload by that user. Parse for the video ID & compare to other IDs you have already logged.
Edited in response to comment
@IamGretar I'd recommend reading about the PHP DOMDocument -> loadXML/loadHTML class to go about this in a decent way, here's a rough and fairly nasty way to do it. This should give you an idea of what you're trying to accomplish, I'm using it demonstrate the principle however, and wouldn't recommend using it for anything else:
$youtube_user_URL = 'http://gdata.youtube.com/feeds/api/users/askhodgetwins/uploads?max-results=1';
$html = file_get_contents($youtube_user_URL);
$pattern = "/<title ?.*>(.*)<\/title>/";
preg_match($pattern, $html, $matches);
print_r($matches[1]);