Back in the mid-2010s, my most rampant polyglot days, I got a lot of mileage out of call-and-response language-learning tapes. Now LLMs have gotten good enough that they can generate this kind of Socratic language-teaching curriculum on the fly. I recommend trying the “Hands free” mode while doing dishes or something. Watch the demo.
Unidex is a pokedex inspired field guide for real life flora and fauna. You take pictures through the app, it IDs and catalogs them, and there's also a quiz mode where you are shown photos you took and you have to pick the correct species name. It's fun and educational! Watch the demo.
This started as an easy-access RSVP speed reader for web articles and EPUBs on my desktop. I actually paid for a speed reader app back in the day but wanted some UX changes, like showing the full page of text for context and being able to paste in URLs. Eventually, I spun off a full iOS app that makes two creative contributions: (1) Speechify-style text-to-speech for web articles and EPUBs in the same app as an RSVP reader, combining all forms of digitally assisted reading; and (2) finger-scrubbing through the full-page context in the RSVP reader, as if scrubbing through a video, but with text instead. This substantially improves my RSVP comprehension, and you can see it in action in the second half of the demo video. Watch the demo.