File this one under “That Was Quick.” Sanwa Japan has unveiled their 400-BT001 Rechargeable Battery that will extend the iPhone 3G an extra 3.5 hours of talk time, 36 hours of audio play, or 7 hours of video playback. The 1,200mAh Lithium Ion device features an LED to measure battery life and comes with a retractable USB cable. At a size of 46×72×13mm and a weight of 50 grams, look for the battery by the end of the month in Japan for ¥4,980 (~$47.00.)