Logitech has unveiled its new Rechargeable Speaker S715i for the iPod and iPhone. The S715i features eight speakers—two three-inch neodymium drivers, two half-inch neodymium tweeters, and four passive bass radiators—a rechargeable battery that lasts up to eight hours, an included carrying case, a 3.5-inch auxiliary input, and a remote control. Logitech’s Rechargeable Speaker S715i will be available this month and will sell for $150.…