This is quite a simple idea, back in 2012 I was reading about how to pronounce Cantonese sounds, and stumbled upon a website that had audio files for every single Cantonese sound. I download all the files, and discovered that there were only about 500 sounds.
That is not many sounds. I realised that I could bundle all the audio files into the application, create a mapping for a character to a sound file and then just play that audio file.
This worked surprisingly well, the resulting audio was quite accurate. Not 100% accurate though because there are Chinese characters that are pronounced differently based on the previous/next character.
So the idea is simple, create an iOS and Android version of this application. It's actually so simple that I could possibly get both apps done in two weeks.