Recently I downloaded an educational app for learning words for kids (from google play store). Very simple: there were a photos of fruits with labels, you could slide them and hear the void speaking the name, and at the end - a quiz. Everything ok, until suddenly a popap with request to purchase the app showed up. Of course at the app description in the store was no information that it is just a demo.
So, I got angry a little bit and sit down and wrote quickly my own version. I used android TextToSpeach feature to easily synthetize the voice. Adding new learning sets is very easy: just put the photos.
Code here: https://github.com/lonski/worducator
And little demo here