For super-powered smartphones, 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.

(Credit: Mophie)

Enter the Morphie 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.

The Mophie Juice Pack is available through select online electronics vendors in Australia.