Does any software exist that will convert singing, humming or wistling into midi tones?

Occasionally a song will come to me and I want to record it, but don't know how to play an instrument. So, I was wondering if I could hum or sing the tune into a mic connected to my computer, record the notes and then use some software to convert them into midi notes/tones. If it can't do that, maybe convert the tones into musical notation, as in written music? Has anyone ever heard of such capability in software/hardware? This would be like someone humming a tune and then someone playing back what they heard on a keyboard.

I checked the faq and did a search and couldn't find an answer.

Thanks, confused