Possibly the most fascinating iPhone app I've heard of yet: RjDj takes in sounds from your surroundings (voices, street noise, tapping on computer keyboards...) and plays it back to you as music compositions in real-time.
Also amusing is the creators' shameless analogy to psychedelics as a selling point:
"The listening experience of RjDj is similar to the effects of drugs. Drugs affect our sensory perception, so does RjDj. RjDj is a digital drug which causes mind twisting hearing sensation."
Check out this video demo:
