WAI-ARIA 1.0 is currently a W3C "Candidate Recommendation".
Developing custom, cross-browser JavaScript widgets is more complex, and implementing WAI-ARIA in these is proportionally more complex.
"WAI-ARIA" is the abbreviation for the Accessible Rich Internet Applications documents. In order to avoid confusion, please use "WAI-ARIA" (instead of just "ARIA"), at least in titles, headings, and on first reference in documentation.
WAI-ARIA is already supported in several browsers and assistive technologies (even though it is not finalized yet). Once WAI-ARIA is stable, WAI will collect and publish a list of WAI-ARIA implementations, that is, what supports WAI-ARIA. Some information on WAI-ARIA support is already available on other Web sites.