There are a lot of apps that having singing lessons. Yousician may be the most popular.
I'd equate being able to speak a foreign language to singing in key. That's what the apps will be able to help with, at least from what I've seen. If that's what you're looking for, that's a good place to start. However, there is a lot of technique to make your voice sound pleasant and interesting beyond just singing on key. I'm not sure if that apps really help out there that much like an actual vocal coach could.
Right, I'm not expecting anything that comes close to a vocal coach - but I'm not dedicated enough to seek one out. I want to spend 15 minutes a day and get incrementally better with some pretty generic tips.
I'd love to get better at singing, but not quite enough to actually find, schedule and pay for singing lessons from a human teacher.
But I'd happily do 15 minutes a day with a Duolingo-style app, especially if it could guide me through exercises to help me sing better.