One constant moan about the iPhone is the length of the battery life; if the quick-fading green-to-red battery bar is a thorn in your side then get yourself a PowerJolt Reserve and never worry about a blank black screen again.
By plugging your iPhone into the detachable Reserve battery pack you can charge both your iPhone or Pod and the PowerJolt Reserve, effectively giving you twice the amount of power every time that you charge. You can unclip the Reserve charger and carry it with you, (it’s small enough to fit into the tiniest of pockets), and when you see your iPhone running out of juice you can simply plug it into the Reserve PowerJolt and it will give your iPhone a well needed boost.
What we really like about this device is that it can charge practically any device that powers up using a standard USB connection; forget lugging around a charger with you everywhere you go, go for the PowerJolt reserve, the most charge that you can get with minimum amount of luggage space.
Link: PowerJolt Reserve
For more recommendations on useful car accessories, have a look at 10 Best iPhone And iPod Car Accessories.