What is Reddit's opinion of Hiragana Cards?

From 3.5 billion Reddit comments

I sorted it out with a flash card app on the Google Play store called Hiragana Cards. Don't be fooled by the name, it covers both kana syllabaries, as well as those... whatever they're called - Kya, Kyu, Kyo, etc. combinations.

Although my advice is to keep the answers covered until after you guess, otherwise it often becomes more a process of elimination.

Beyond that there's NHK Easy News, which usually includes articles with enough katakana for you to practice with.