Yesterday I was presenting Musescore to a friend. And he asked me if the program had something like a "spell checker" but for music, like a chord checker. Actually, I found the idea really interesting : it could be an option that the users could activate or not, and it would, for example, underline a group of notes (of the same scope or not) if they play a chord that exists (i.e. Am, Gb7, ... etc.) or not (and the user could choose to add it to his database.
All the program would have to do is looking at every note which is played at the moment T, and look if it exists or not.
I think this idea could help me (and probably other people too) a lot, because sometimes I work on pretty complex music (orchestral music, with dozens of instruments), and it is sometimes hard to do a chord prooerky, because when I listen to it, it seems ALMOST alright, but there is sometimes one instrument which plays a wrong note.
Hope the idea will interest you (and sorry for the English mistakes, it's not my mother tongue ^^').