samples/ApiDemos/src/com/example/android/apis/accessibility/_index.html

<h3 id="Accessibility">Accessibility</h3>
<dl>
  <dt><a href="ClockBackService.html">Accessibility Service</a></dt>
  <dd>
    This is an example of an accessibility service that provides custom feedback for the Clock
    application which comes by default with Android devices. It is a hands-on example of various
    ways to utilize the accessibility API for providing alternative and complementary feedback.
    The sample demonstrates how to provide application specific feedback &mdash; the service
    handles only accessibility events from the Clock application. Further, the sample demonstrates
    how to provide dynamic, context-dependent feedback &mdash; feedback type changes depending on
    the ringer mode.
  </dd>
</dl>

<dl>
  <dt><a href="TaskBackService.html">Window Querying Accessibility Service</a></dt>
  <dd>
    Demonstrates several new accessibility features in Ice Cream Sandwich,
    including the ability for an AccessibilityService to traverse the view
    hierarchy using AccessibilityNodeInfo objects, service configuration via
    xml files, and adding additional information to AccessibilityEvents using
    AccessibilityRecords.
  </dd>
  <dt><a href="AccessibilityNodeProviderActivity.html">Accessibility Node Provider</a></dt>
  <dd>Demonstrates how to develop an accessibility node provider which manages a virtual
    View tree reported to accessibility services. The virtual subtree is rooted at a View
    that draws complex content and reports itself as a tree of virtual views, thus conveying
    its logical structure.
  </dd>
</dl>

<dl>
  <dt><a href="CustomViewAccessibilityActivity.html">Custom View Accessibility</a></dt>
  <dd>Demonstrates how to implement accessibility support of custom views. Custom view
      is a tailored widget developed by extending the base classes in the android.view
      package. This sample shows how to implement the accessibility behavior via both
      inheritance (non backwards compatible) and composition (backwards compatible).
  </dd>
</dl>