Tenon.IO is for automated accessibility testing, it is still in a private beta but will become an open public beta this Wednesday, though you can test anything right now via http://tenon.io/index.html#testnow with a URL or direct HTML copy and paste.
A Grunt tool I am lead to believe will be made available, and for some background on Tenon IO and their plans the following articles should help:
http://www.karlgroves.com/category/accessibility-testing/
The accessibility team, of which Karl Groves is a contributor touched on it earlier this year:
Accessibility Team Update: May 7, 2014
I’ve been in the private beta of Tenon.IO since it kicked off and it is extremely helpful to say the least, bbPress has always tried to be accessible, though keeping up with “everything” accessibility is not easy, we’ve a few patches ready to add to bbPress based off of this testing here.