PPYPLE offers Active Case AC5 for iPhone 5 and 5S. It features an external antenna to improve RF performance while grip and calling and thus saving 10% to 15% battery life time. The embedded RF module further improves the sensitivity in 850 MHz that also helps saving the battery. The Active Case not only provides signal boost external antenna and RF card slot but also offers the complete anti-shock protection for your iPhone 5 and 5S.
Available at amazon.com for $13
