(I asked this earlier, but submissions can fall off the front page quickly, and I'm submitted at a different time to try to hit a different HN demographic.)For interest, I and some colleagues have written a "Chat" app. Think SMS, but with extra features that make it "interesting".
It's end-to-end encrypted, distributed, resists traffic analysis, decentralised, and generally we're finding it a useful alternative to existing alternatives.
We have our own ideas about what to add next, but it's probably the right time to get out of our fishbowl and get ideas from a wider potential audience. We're not looking for reactions from the world in general, this won't ever be used for sharing pictures of cats or videos of pratfalls, so I suggested to my colleagues that HN might be the place to ask for opinions on what might be regarded as essential.