George, I am trying to avoid one language learning. We become too narrow minded if we focus only on one language. If I had been introduced to Spanish, French, Italian, and German collectively at a beginner level I might have chosen one language to become stronger in. It's actually easier for me to study Korean by using Chinese and Japanese. I am trying to find a way to learn a family of languages like a musician would play one instrument in a group, but they would be exposed to the other instruments. When you read about European history, you don't just learn about one country. Same idea. Before you decide on one language, you should really spend time getting a taste of several.
As for pronunciation, people should study with a native speaker. If that is what you want. The last thing I want to do is train myself to be dependent on an iphone app to communicate. I don't own an iphone, I don't want an iphone, and I don't believe it is healthy to learn from them. It's like eating microwave food. It's fast and available, but is it really good for you? Which area of China are these tones from? Chinese pronounce words differently depending on where they are from. Does the app fully address this issue? I highly doubt it.
Google "Glossika" and check out his youtube videos. His lectures/lessons would rip any app into shreds. Here's one http://www.youtube.com/watch?v=CK7TkeK-hOk