Microsoft has announced the availability of a Microsoft Word add-in (Word 2007, Word 2003, Word XP) for saving OOXML-based Word documents as "DAISY XML." It's available for free at http://www.openxmlcommunity.org/daisy/.
DAISY (Digital Access Information SYstem) XML is the foundation for supporting digital talking books. It works by linking sections within an XML file to points within a corresponding digital audio file. By using special devices or by installing special software on PCs, users who are blind or have poor vision can jump to specific sections in the audio stream or skip over footnotes altogether. This is an improvement over having to listen to the audio serially.
While the Word add-in is OOXML-based, there are ODF initiatives for generating accessibilty-friendly documents. The DAISY Pipeline (as described by DAISY; as described by (SourceForge) is an open source project for performing DAISY-related transformations (including ODF to DTBook). In addition, the ODF Accessibility Guidelines offer an ODF-based foundation for generating accessible documents. However, these two initiatives are developer-focused, giving programmers tools that help them create products that will generate accessible documents. Today's Word add-in cuts to the chase, giving end users with disabilities something they can use today.
Whether ODF- or OOXML-based, such products and initiatives highlight the value of XML over binary formats. Because XML teases out the underlying structure of a document, it makes jumping from section to section or object to object easier than it was in binary formats (which are inclined to treat a document as a serial, undifferentiated thing). Put another way, XML embeds more intelligence within documents, and that's a good thing.