From Tom MacWright:
heard is a native Mac application that sits in your menu bar and records what you listen to in iTunes.
It's the small part of last.fm that I want. It records when you start a song, how long the song is, the artist, et. cetera. It's anti-social, has nothing to do with the cloud, and the use case is less precise than 'social sharing and discovery': the main end-product is the ability to export your songs to JSON.