(excuse my English ! French speaker here)
I use Lingvist (Russian from English) in front of my computer or iPhone. It's relevant to increase my orthographic skills (computer with keyboard input) and oral : iPhone with Siri, and even writing with My Script - Stylus, but this last is tedious.
But there a lack, in immobility, my blood doesn't circulate enough to learn efficiently ! :)
So the best feature everyone is waiting for (crowds noise here) is an audio file generated on the basis of the list of sentences that one might repeat, with blanks to give a room for. And the heavens would be to generate an SRS-like sequence of i.e. 15 minutes a day in 15 files.
Indeed, I find it's more relevant to get back to a text from an unmastered sentence in an audio I have problem to remember or understand, beacause from a text, it's eventualy too easy and I less realise that I don't remember.