To help blind and vision-impaired users use Nexus 7 more easily, Google offers the Android Accessibility Service in the tablet, including TalkBack, Kickback, and SoundBack. To use text to speech functions (TalkBack), you can enable it to help you navigate through the tablet if you have trouble seeing.
* Go to Settings. You can go there from the Apps screen, or drag down Notifications and tap on Settings icon.
* Select Accessiblity under SYSTEM at the bottom of the screen.
* Touch TalkBack option and turn it on. Tap OK when it prompts.
TalkBack works fairly well but no easy shortcut to turn on and off,