Anyone can recommend text-to-voice-file apps?

Hi everyone!
On the Windows platform, there's a free software called Balabolka, which uses the voices on board the system, and can convert and make audio files. And, best of all, it's free.
Now, I would also like this kind of service on iOS. Is there a similar kind of app that would do this magic? I use the files just for my own listening, and also for offline use on my MP3 player (so, in short, I like the files to away from the iPhone).
I'm seeking some app recommendations, if any!
Many thanks!
David