This one's for the musicians out there. ScoreCleaner Notes allows you to play, hum, or even whistle a tune, and it will write out the musical notation for you, including the correct time signatures. It can even pick apart multiple voices at once and arrange them in the proper order of lead voice, second voice, and bass line.

After these notation sheets are created, they can be edited and/or shared with others. You don't even have to know how to read notation to create your own music score, and I think that's amazingly cool.

The app only costs 99¢, but you can see it in action here before buying.