Remind. Secure. Find. Those are the three benefits that Kensington is promoting with its new BungeeAir Power Wireless Security Tether for iPhone 4 ($100); we’d tack “Charge” on there as the fourth verb. This new iPhone 4 battery case and security system — composed of a case, keychain fob, and app — is designed to help a user keep tabs on an iPhone 4, and prevent it from accidentally being left behind. A 1500mAh rechargeable cell is built in to make the case more appealing.

The BungeeAir case resembles the company’s earlier PowerGuard, and separates into two pieces: one is the back plate, which holds the battery and plugs into the iPhone 4’s Dock Connector port, while the other is a plastic frame that snaps into place and protects the device’s sides. It should be noted that while the pieces snap together, and there’s a sliding mechanism to hold the front frame in place, there’s no physical lock that prevents them from coming apart in the event of loss or theft; similarly, while the headphone port is open for connections, and a USB cable is included for recharging the case and your iPhone at the same time, the expectation is that you will remove the iPhone 4 when connecting other accessories, such as speakers or docks. Like PowerGuard, there’s coverage for the volume and Sleep/Wake buttons, and we like the feel of them quite a bit. One issue we noted was that the paint on the back of the case, specifically around the camera, started chipping away after only a few days of use.
Although the two piece, snap-in design isn’t as sleek as some other battery cases, it serves a dual purpose.
When the frame is in place, it depresses a small white button right below the Dock Connector port. When the case is removed, this button is triggered, sending a signal to the fob that may alert you to possible theft. Also unique to this model is a built-in alarm speaker located at the top right corner. Notably, Kensington also includes a plastic card that can be used as a stand by sliding it into a slot on the back. The company suggests that you can also use any credit card for this, although we’d be cautious due to the small risk of accidentally demagnetizing your cards.
We tested the battery under our standard conditions: a powered-on, 3G/Wi-Fi-connected iPhone 4 with the screen turned off, no calls coming in, and no audio playing. The result was an increase from 9% to 81%, a charge of 72% that took just under two hours. That figure is right around average for a 1500mAh battery, although we’ve seen similarly specced batteries give up to 13% more charge, and some fall lower than that. It’s worth noting that Kensington also offers an $80 version of the case without the battery, called BungeeAir Protect Wireless Security Tether. In other words, the battery is added for a $20 premium, which we’d say is worth the added expenditure over the base BungeeAir model.
The unique idea behind the system is that the case and fob create a “wireless tether.” If they’re separated from each other—say you leave your iPhone 4 on a restaurant table and walk away from it—the fob will vibrate and chime to alert you that the tether has been broken. The distance is about 50 feet, depending on the environment.
Breaking the tether also puts the phone to sleep. Kensington recommends setting a passcode to trigger immediately when the iPhone 4 is in sleep mode, so as long as that setting is in place, breaking the tether essentially locks the device. Although these precautions won’t prevent your iPhone from being stolen, your data won’t easily be accessed.
In addition to the tether, the fob and case can also be used to find each other as long as they’re in range. Pressing the alert button on the fob triggers the alarm in the case to sound. In our testing, whenever we triggered this, the iPhone 4 would also start playing music, and we’re pretty sure it’s not supposed to work that way. The find feature on the iPhone is controlled through the BungeeAir app, a free download through the App Store. It offers two different controls as well as Settings and About menus. From the app, users can arm or disarm the system. When it’s disarmed, none of the notifications will go off.