"Now besides simply searching on the metadata of the video files, you can search for terms that are actually mentioned inside the audio, allowing for a greater likelihood you will find relevant material. We're also automatically organizing the videos into channels based on the actual content of the video. Today you can narrow your search within entertainment, sports, and anime. And we'll continue to add more," promises PodZinger Blog.
A search for "youtube" on PodZinger shows 286,132, so we can assume that's the number of searchable videos. Unfortunately, you can't go directly to the section that contains your query, so you'll have to watch the video from the beginning.
I wonder if YouTube doesn't mind that PodZinger processes their videos. Google Video also does this, but only for videos that have captions.