Hello,
One year ago, after two years struggling with the russian language, i started to apply a new method and then built a web site in order to apply it very comfortably.
The metod is based on the repetition of short texts, following a precise time schedule.
You can find more information in the web site, that is still free:
http://www.repetita-iuvant.com
It's not an app but the web site (the practice section) is optimzed for a smartphone screen.
In the home page there are two videos where I explain the method, one in russian and one in english.
Paolo