I found Lingt very similar (in concept) to Anki, which has an iPhone client. I do not have an iPhone, so I can't tell how good it is, but Anki (desktop) is fant

I found Lingt very similar (in concept) to Anki, which has an iPhone client. I do not have an iPhone, so I can't tell how good it is, but Anki (desktop) is fantastic. I am currently learning Mandarin, and Anki is my primary resource for vocabulary memorization.