Getting ready for my trip to the Macworld Expo I wanted something that would stay in place dependably no matter where I put it, so I went back to Monoprice.com, and found a leather case cover with a 2200 mAh battery built in that the iPhone snaps into. The price is ridiculously low at US $20.75, just US $5.52 more than the dongle. This has been on sale for at least as long as the dongle, I hadn't heard anything about it, but decided to give it a try.
What you get is a plastic case housing the battery that your iPhone 3G or 3GS snaps into. iPod touch users need not apply, since when plugging your device into the case, you'll be covering your speaker jack, making the product worthless to you. Connected to the top of the case is a leather cover that you flip to protect your screen. On the left side is an input for the usual 30 pin dock cable to charge the unit. On the front is one light and a toggle switch marked on and off. As is usual with Monoprice, there are no instructions.
You really don't need instructions since it's pretty obvious how it works. Slide your iPhone onto the case's 30 pin dock connector and the fit is nice and snug. Plug in a standard iPhone/iPod cable into the side and the light turns red until fully charged when the light turns green. The on and off switch activates or de-activates the battery backup. I can't come up with a good reason to ever turn it off. The leather flip cover not only protects the screen, but also acts as a stand, when folded back a bit, holding the iPhone upright in either landscape or portrait mode. So much for those little flexible plastic holders. Another nice feature is that if you leave the switch set to on, you can charge both the battery backup and your iPhone at the same time using a standard 30 pin iPhone/iPod cable.
Its closest competor is the Mophie Juice Pack which has a smaller 1800 mAh battery, needs a mini-USB cable to charge, has no screen protection and costs $US 99.95. In its favor though, the Mophie comes in four colors while Monoprice ships only basic black.
The downside of the Monoprice case: It adds a good deal of heft to the svelte iPhone. Batteries aren't light. The upside is that it's US $79 cheaper than the Mophie with a larger battery, screen protection, and you don't need to find that missing mini-USB cable. You'll also save another few bucks by not having to buy a stand. As with anything else I've bought from Monoprice, I recommend it highly.