Ask HN: What API or app-based service do you wish existed – and would pay for?

I'm curious: what kind of API or app-based service doesn't exist yet (or isn’t widely available), but you would gladly pay for if someone built it?

Think of tools, data, integrations, or automation you’ve looked for but couldn’t find — whether for developers, creators, businesses, or personal use.

What’s missing from the current ecosystem?