Will the sample sentences have features like for a user with knowledge of just 500 chars and 600 words the application just throws a basic sentence having all the words from his knowledge?
For an advanced user at the same place the sentence could be tougher. This will sort of build graded reading into the app.

Nick .. inputs?

This is what we are hoping for!

Hoping they can scrape something up like this. Of course, I study Japanese, and I think I remember them saying they might not even be able to do Japanese example sentences, so I'm hoping I get any functionality in this regard at all, hehe.

I would love a sample sentence based on level of characters known.

I imagine it would be a mountain of work finding suitable sentences for every word though.

We haven't worked out the technical particulars of the example sentence system but that's one of our goals, yes! Also being able to study them would be good.