The battery, which needs to be manually installed, is priced at ¥3,150 (around $31), and dated for July 25 in Japan. When approached, a Nintendo spokesperson told us today's reveal is specifically a "Japanese announcement," and that "all other territories will make announcements if relevant." So we'll have to wait and see if the battery's coming west.
Also getting a power-up is the Wiimote, via a new fast-charging pack. Nintendo promises the pack, which includes a new battery, backplate, and charging stand, both charges the peripheral quicker and for longer. Wii and Wii U owners in Japan can buy the upgraded battery alone for ¥2,625 ($26), or get the whole pack for ¥4,200 ($41).