As an alternative to waiting for browsers or mainstream assistive technologies, such as screen readers, to provide MathML accessibility, protocol handers could be used to enable external applications to provide functionality specific to the rendering, reading, navigation and manipulation of mathematical expressions in MathML.  In the example HTML markup below, we have an image of an mathematical formula that is hyperlinked with a proposed math: protocol handler that passes the application handling the protocol a URL to a web service or web page that contains the representative MathML markup:

<a href='mathproc://mathmlcloud.org/m/someuniqueformulaidorhash'><img role='math' alt='a equals x squared' src='imageofformula'></a>

In the example above, the anchor tag is enclosing an image element, because images are a broadly supported and common fallback to the display of mathematics on the web.  However, the anchor tag could enclose MathML markup that is or is not combined with the MathJax polyfill JavaScript library to provide visual rendering.

MATH PROTOCOL HANDLER COMMUNITY GROUP

This group's aim is to discuss and agree on the use of a custom protocol handler (math:) and standard parameters for enabling the export of mathematical expressions in MathML to other applications, such as assistive technologies, graphing calculators, math notebooks and other mathematics oriented applications, such as IPython and MATLAB. For more information, see https://wiki.benetech.org/display/MATH/Protocol+Handlers+for+External+Applications+to+Process+MathML