For super-powered smart phones, battery life is kryptonite. All that 3G Wi-Fi GPS wonderfulness leaves batteries exhausted, especially after they've starved themselves thin to fit into the sexy form factor.
Enter the Mophie Juice Pack, a rechargeable lithium polymer battery that says it will add up to an additional six hours of talk or surfing time to the iPhone.
It's a green and black shell that cradles your iBaby in a soft, almost rubbery grip, like a friendly alien face-hugger. We found it comfortable to hold and handle, although it added about a centimetre of thickness to the phone, so it wouldn't suit someone with tiny hands.
It has pass-through USB for syncing and charging, which is very handy, because you can charge and sync your iPhone with a standard mini USB cable -- of which we have dozens in our drawers -- rather than carrying around the iPhone's proprietary one.
We have a theory that the Juice Pack is made of Higgs bosons -- it has an odd relationship with gravity. At 75g, it feels light as a feather, but it when it docks with the 135g iPhone 3G, their combined mass is extremely hefty. We wouldn't want to carry it in our pocket for a night out -- its weight would ruin the line of our silk smoking jacket.
But the Juice Pack is a great accessory for a long road trip. We would have loved it while roaming Cornwall last weekend, draining our iPhone's life force with Google Maps and surfing the Web for the best local pint -- especially when we ended up stranded on the hard shoulder praying the battery would hold up until the RAC called.
Update: You can buy the Juice Pack at Mophie's Web site for £68 for the iPhone 3G version, or £64 for the second-gen iPod touch version.