Apple today introduced the anticipated fourth-generation iPod nano. The model is said to combine the best of the second-generation player's shape with the large screen and video playback of the third-generation model but is even thinner and adds an enhanced, accelerometer-driven interface that rotates the on-screen interface; this improves the use of Cover Flow and even photo browsing, Apple says. Users can even shake the player to shuffle tracks similar to SanDisk's Sansa Shaker.

The new software also automatically builds in voice recording and has a context-sensitive menu that appears just by holding the center button.

Apple claims the same 24 hours of audio and four hours of video as with the third-generation player, but also a more environmentally-friendly device with an aluminum exterior, arsenic-free glass and toxin-free internals. It's the "cleanest iPod ever," Apple chief Steve Jobs says.

The nano will ship in an 8GB model for $149 and a 16GB version for $199; nine colors will be available and include more exotic colors such as orange and yellow. Most models should be available by the weekend, though the 16GB may be delayed to early next week.

Apple is also introducing new high-end earphones with a built-in play/pause control that works similar to the iPhone's: double-clicking skips to the next track, while three clicks skip backwards. The optional earbuds cost $79 and come with three different fits for different ears.

Additionally, Apple has also announced a slightly upgraded iPod classic; the company is scrapping the 160GB model and now just offers a single 120GB model in silver or black. It will sell for $249 and should be available in a similar timeframe.