I'm using Rocksmith and Yousician (the free version), but I think there's room to improve over what both of them provide for practice / exercises. For learning and performing songs they're definitely the best due to the sheer amount of content they have.
I'm very early in my learning journey so I'm not concerned that developing a prototype version I could use for myself will take too long (it could be that I'm underestimating the difficulty of the problem). I was already able to slap together most of the "glue" code in Unity in a couple hours, and given my signal processing background I have solid ideas for how to approach the difficult algorithmic parts.
