Comparing sound on external device with the microphone to existing audio file

I was wondering if this is possible with Unity3d: I would like to sync events in my app with a Youtube video that is being played back.

E.g. I have an audio track of a video that has to play on Youtube, or on TV. I would like my app listening to that sound and try to compare that with the original (same) audio track. The purpose is to calculate by using sound where the playhead of the Youtube exactly is, in order to let my app respond 'live' to the video.

Is this the right approach, or are there better ways to achieve this goal? And if so, can anybody point me a little bit in the right direction?