We like to bring readers details on smartphone accessories and have given plenty of details before about various battery cases. Today’s accessory news is a little different though as it’s an iPhone 4 / 4S battery case, the Spyder PowerShadow i4, that also features a handy dock and comes at what we feel, although not cheap, is a reasonable price.

A problem that many of us face with our increasing reliance on our smartphones is battery life and this case alleviates that problem as well as providing good-looking protection. The Spyder PowerShadow i4 Battery Case & Charge/Sync Dock is for the iPhone 4 or iPhone 4S on either AT&T or Verizon and will glean the optimum performance from your iPhone with its additional battery power. Charging and syncing can be carried out in the dock without removing the iPhone from the case with a variety of options, making this a useful iPhone accessory.

This battery case and dock is lightweight, with an ultra-slim polycarbonate body and satin rubber finish for a premium look and feel. The battery’s 2000mAh battery is capable of providing 8 hours of extra talk time on 3G, 11 hours of video or 44 hours of music while still providing the user access to the iPhone’s controls and ports. It features a battery level indicator, on/off button and there’s also an optional in-car charger available. In the package you’ll find the Spyder i4 battery case, the charge/sync dock, USB cable and a guide.

Dimensions are 5.01-inches x 2.4-inches x 0.79-inches and it weighs 73.7 grams. If you want to find out more or order the Spyder PowerShadow battery case and dock then head to Spyderstyle.com here where you’ll see it’s priced at $89.99. As we said previously this is not a low cost accessory but it does seem a reasonable price for what it is.

Over on ZDNet there’s a full review of the i4 battery case and dock and the convenience of having the dock with the case is noted. Every part of the iPhone except the case is covered but the extra weight was seen as a possible drawback for some users, even though the reviewer felt it was “solid in the hand rather than too heavy.” It was also noted that this case, with a battery bigger than the battery in the actual iPhone, was able to provide the reviewer with 2 or 3 days of “heavy use.”

The overall verdict was that this case is unique, convenient and worth the downside that it doubles the thickness of the iPhone. We’d like to know what you think about the Spyder PowerShadow i4 battery case and dock for iPhone. Do you feel the price tag is realistic? Maybe you’re planning to purchase one right now? Let us know with your comments.