TTS on Android/ iOS

Android 1.6+ has built-in TTS (Default Engine: pico TTS)

SpeechSynthesis Data Installer is required before TTS can work.
To install:
Select device Setting >Voice input and output > TTS Settings > Install voice data

App with TTS feature:
Cool Reader


On iOS, Setting > General > Accessibilty > Triple-click Home > set to "Ask"
Open ePub in iBook > triple-click home button > select Voice Over On

Set language for TTS Engine (tested on Android only)

In case of the  Utterance module, use the following:

var speech = Utterance.createSpeech();
speech.startSpeaking({
  text: 'tex to read',
  voice: 'en_US'
});

It's calling the Android  API TextToSpeech.setLanguage(locale) at the back.
Possible values for the above voice = possible values of java.util.Locale

e.g. zh , zh_TW, en, en_GB, en_US, etc.

List of possible values