Energizer (http://www.chargeyouriphone.com) has introduced the AP1201 for iPhone 4. This rechargeable case with built-in battery purportedly supplies nearly twice the power of the iPhone, while offering protection that you never need to remove.

The AP1201 has “smart” battery technology that auto senses the iPhone 4 battery power status that’s indicated through “hidden” LED’s on the back of the case. For power management, two charging options provide either high speed quick charge direct to the iPhone 4, or get simultaneous pass-through charging of the iPhone and AP1201 case. The AP1201 is rechargeable up to 500x and comes with a USB charging cable.

The AP1201 is a one piece case, manufactured with form-fitting recycled silicone rubber that’s durable, extremely thin and lightweight, says Jim Olsen, vice president of marketing for Energizer North America. The low profile case is silky smooth to the touch, yet non-slip and fingerprint resistant, he adds.

What’s more, the AP1201 also features an integrated bumper that eliminates the signal loss and antennae interference issues that some iPhone 4 users have experienced. It’s available now for a manufacturer’s suggested retail price of US$69.99.