Language learning with an augmented messaging app

I'm thinking more and more about the language learning that can take place within a conversation via a messaging app, especially when augmented by Google Translate. I started writing about this in a previous post and I'm going to add a few more thoughts here. I've been practicing my Spanish with a family member who speaks fluently. My current ability wouldn't allow me to say very many things of interest; however, by leaning heavily on Google translate, I can pleasantly converse about quite a bit. It seems to be a valuable learning experience. Most tout conversation with a friend as the very best way to learn a language and, indeed, my vocabulary and ability to understand and participate in simple dialogue seems to be improving from this practice. Yet, there are definitely some ways that this experience could be improved in an application. Most obviously, I'd like to be able to translate into a target language directly within the messaging app. It'd be nice to employ some kind of currency system that would offer incentives for a user to use the target language when they already knew the needed words/grammar, etc. When the user was writing in the target language, it would be helpful for them to see, or maybe have the option of seeing, their writing translated back into their own language. Using a word in the context of meaningful dialogue is an excellent way to learn. However, just seeing it once or twice is usually not going to be enough to remember it long term, especially if the translation was pretty easy to come by with the automatic translation service. To reinforce the learning, new words should be noted by the messaging app and simple practice activities given to the player at regular intervals to practice them. These practice activities could automatically generated from the dialogue itself. They could be as simple as fill-in-the-blank activities using the original dialogue and several new words that had been noted (including the one correct answer). They could also jumble sentences and have the player rearrange them, using the context of the conversation as guide. Another very useful feature and important for learning would be the ability to flag a message in the thread as potentially wrong, and the ability to discuss the message and edit it without disrupting the flow of the conversation. So some way to flag and comment is important. Even better, and potentially a way to monetize, would be a flag calling paid human editors to give the message a pass. Big questions to answer: Can you sell an app that's using the Google translate service? Could they come steal your IP if they wanted to? Could you integrate something like this into Facebook messenger to take advantage of its user base?