Synchronizing text and audio. Is there a NLP/speech-to-text library to do this?

I would like to synchronize a spoken recording against a known text. Is there a speech-to-text / natural language processing library that would facilitate this? I imagine I'd want to detect word boundaries and compute candidate matches from a dictionary. Most of the questions I've found on SO concern written language.

Desired, but not required:

• Open Source
• Compatible with American English out-of-the-box
• Cross-platform
• Thoroughly documented

Edit: I realize this is a very broad, even naive, question, so thanks in advance for your guidance.

What I've found so far:

• OpenEars (iOS Sphinx/Flite wrapper)