I wrote a simple app that takes context sentences from wanikani and presents it as a quiz. It should work on both mobile and desktop. You can try it here:
https://michaelboyles.github.io/wk-context/
Someone recommended this similar app but I wanted some features that it didn’t have and it isn’t open source, so I wrote my own.
I wrote it to use as part of my own study but I hope someone else can find it useful too.