Price: $215/18,000 Yen
Compatible: iPhone 3G/3GS
VentureCraft Go-DAP Battery + Headphone Amp Jacket for iPhone 3GS/3G
It's surely a niche offering and quite late in the game for U.S. release as an iPhone 3G/3GS accessory, but Japanese developer VentureCraft's Go-DAP Battery + Headphone Amp Jacket (18,000 Yen/$215) is unlike any other iPhone accessory we've seen. Fusing together a 1450mAh battery with an integrated headphone amplifier with 300mW/16 Ohm power and 0.009% distortion at 10mW, the metal and plastic frame slips onto the back of the plastic iPhones and enables hard-core headphone users to pull and attenuate audio from the Dock Connector port of the older iPhones, with up to twice the iPhone 3G's standard capacity and arguably higher sonic fidelity when coupled with inefficient headphones. The integrated battery enables the amp to run off of its own power rather than draining the iPhone's, and Go-DAP can be either recharged or synced by connecting the included mini-USB cable to a computer. Additionally, the rugged metallic industrial design is amongst the best we've seen for a portable amp; somewhat similar options disappeared several years ago with the introduction of the iPod classic, but used to be pitched to audiophiles before then.