From Thanko Japan comes the USB powered noise cancelling earphones. The main unit is is the size like the 1st generation iPod Shuffle, it connects to the MP3 player via 3.5 mm plug. The ear buds have a mic which guage the level of ambient noise levels once the noise cancelling feature is turned on and then send an equal but opposite canceling signals to the earphones. The Lithium Ion battery provides 15 hours of playback with noise cancellation, it charges fully in 2 hours.
Thanko noise cancelling earphones are available in Japan for 4280 Yen ($ 35)