Dec. 1, 2011 -- Owners of the iPhone 4S know just how quickly the battery can be depleted, even with Wi-Fi and Siri turned off. Luckily, there are so-called "juice packs," cases that hold an extra charge to keep your power going all day long, so your smartphone can keep up with you.
The PowerSkin Silicone Case with Built-In Battery is a simple case made of recycled silicone rubber that fits over your phone and protects it from accidental bumps and drops. It's thin enough that it doesn't add too much bulk, so it doesn't take away from the sleek lines of the iPhone.
The non-slip grip helps you hang on to your phone even when the battery is running away, and that's when the extra power of the PowerSkin kicks in. The case has a built-in 2000mAh capacity battery that essentially doubles the battery power of your phone. A switch on the bottom tells the case when to start powering the phone; you can choose a constant charge, or wait until your phone truly needs it. LEDs on the base of the case let you know when it's time to recharge the PowerSkin's battery (via micro USB) so you're powered up and ready to face another day.
The PowerSkin is also available for many Android smartphones as well as BlackBerry phones.
The Third Rail: A new concept for mobile power, this $90 device gives you a case you can use on its own and a battery that snaps onto the case to provide extra juice. You can also purchase more batteries and stack them, adding more and more battery power. Each battery has a capacity of 1250mAh, which is about 80 percent of the iPhone 4S's battery capacity.
Its workings are simple. Each battery has two ports: one for charging the battery (via micro USB) and one for sending the power back out. What's unique is that, in addition to charging the iPhone, the battery on its own can be used to power just about any device, such as an iPod, a Bluetooth headset or a gaming device, all using the included micro USB cable. You can purchase extra batteries for $60.
The LifeProof iPhone case: If you take your phone everywhere, and that includes to the beach or to the desert, then this case is for you. The case promises to love, honor and protect your iPhone if you drop it in water, bury it in the snow, or take it through a sandstorm. All that and it adds just 1.5mm to the iPhone's depth. It weighs less than an ounce and is priced at $80.
The company says the case is waterproof to 6.6 feet, and the double AR-coated optical glass lenses mean you can take it in the pool or ocean, and even use the phone's camera to take pictures or video underwater. LifeProof says the case permanently seals the phone against exposure to mud, sand, grit, dust, and lint which are a particular problem when minute particles get between the case and the device.
You can access all the phone's features with the case on, and of course use the capacitive touch screen. To keep the elements out of your headphone jack when not in use, the case comes with a cover that screws into the headphone jack's opening.