Japan Marketing News wrote about kairo, the omnipresent disposable pocket warmers favored by so many Japanese during the cold winter months (Kairo keep Tokyo Warm). They’ve been a mainstay in Japan for decades.
In retrospect, it’s amazing that somebody else hadn’t already thought of it, but in late 2006 Sanyo introduced a rechargeable kairo that employs the company’s eco-friendly eneloop batteries.
Once charged, they stay warm for up to seven hours and they can be recharged 500 times. An on-off switch lets you put on the heat whenever you want. They’ve definitely caught on and sales are expected to be three times higher than last year. They sell for about 4,000 yen at major electronics shops and about 75% that on Japanese online shopping sites like Rakuten.