TTSOverview-iOS is a project mainly written in Objective-C, it's free.
A simple application for comparing iOS-compatible Text-To-Speech solutions. Build for iPhone 4.3
Free BSD-like licensed Text-To-Speech engine. THX https://github.com/jeska/eyesfree_dev iOS-adopted Flite version.
Is you are going to use many languages, additional efforts required.
You know it.