Italki is a very nice website.Does it have an app for phone?
They are still working on it. I've noticed that the android version has come out, so it won't be long to see ios app.
I think they have not any app
According to this, only for Android
http://support.italki.com/hc/en-us/articles/206351418-Does-italki-have-a-mobile-version-or-app-