This sample demonstrates how to create a text to speech engine that users can install on their devices.
The application includes a service and two activities:
RobotSpeakEngine,
    a simple text to speech engine that converts sentences into audio by
    generating a square wave of a given frequency for each alphabet of a
    given language. Though this doesn't qualify as speech (except for robots)
    it exercises all aspects of the new text to speech API
    by subclassing the
    TextToSpeechService
    framework class.
  CheckVoiceData,
  an activity that checks that all voice related data is installed and
  available.RobotSpeakSettings,
    a settings screen for users to set various engine parameters. This is
    usually accessed by users from the system wide settings app. This must be
    declared in the AndroidManifest.xml file as a
    meta-data element.Note that this API is supported only on Android 4.0 (API level 13) and higher versions of the platform.