Probably not feasible but I've always thought an app that graded your ability to sing along to your favorite music would be fun. Being able to automate the isolation of the vocal track to judge the user against would obviously be required, so it's nice to see some advancements in that direction.
There’s plenty of video games that do this going back to 2003’s Karaoke Revolution - if not earlier. Plenty of other games and series followed suit including as Rock Band, Guitar Hero, Lips, SingStar. There’s plenty of mobile apps that work similarly. AFAIK they basically track your pitch and timing. I remember Lips in particular rewarding vibrato as well.
The algorithms as I understand them are grading you based on sustained pitch (adjusting for octave) and cadence. Generally they are easy to fool - you can basically say gibberish but as long as it’s within the expected parameters you’ll still get a good score.
They are still rather fun though if you enjoy that sort of thing.
