Singular Software already offers PluralEyes, a plug-in that works with Final Cut and other NLEs to sync video and audio clips by analyzing the audio tracks and matching them.
Now they have released the first beta for DualEyes, a standalone application for the automatic synchronization of video and audio clips for dual-system audio production. According to the release, DualEyes is similar to their product PluralEyes product, but is streamlined for the task of replacing in-camera scratch audio with separately recorded high-quality audio.
So, my understanding is that DualEyes is a standalone app that will take an audio clip and match it to a video clip, while PluralEyes is a plug-in that will match multiple clips...
Singular Software: DualEyes Product Page
Singular Software: Downloads