HelloChinese has Duolingo addon
Some learners have already suggested HelloChinese for writing practice with the Chinese characters. Others have pointed out that "painting" the character on your phone with your finger is a less than optimum method for learning the art of calligraphy (ok) and that learning to type the characters is becoming more important than learning to write them (yup).
But brushing that debate aside, I just noticed on the HelloChinese app on my iPhone, that when you choose: "Learn" from the bottom menu bar and then choose the menu icon in the upper left corner, you'll see under "Add-ons" the choice "Duolingo Characters". It's the fantastic review tool I've been needing!
Characters are arranged according to the Duolingo lessons. You have a review card for each character with audio, pinyin, definitions and squares to practice writing. (TinyCards and Memrise are great, but this add-on is just what I needed for Chinese.)
I'm a rank beginner with Chinese, so if any of you pros know of similar or better review tools that coordinate with the Duolingo lessons, I'd love to hear about them.
If you practice with a computer, YellowBridge also has a great feature that allows you to type in a character and practice its strokes, pronunciation, get the meaning, etc.