I had a problem with my mini battery extender, so I contacted support via email. All I got was nonsensical responses, except for one gem of information. THE PRODUCT ONLY WORKS WITH 2.0 FIRMWARE, NOT 2.1 OR 2.2!!!
They also will not answer any further inquiries when I have tried to find out when or if they will resolve this issue. Since I didn't know this, and I had the product more than 30 days, and didn't keep the original packaging, Kensington, and my original vendor, will not accept a return, and also will not replace it (although replacing it will not do any good anyway).
Without 2.1 or 2.2 support, this device is useless. Buyers should be aware of this before they buy, not after. Kensington support refuses to respond any further. They did state, in writing, that it doesn't work with iPhone running 2.1 or 2.2. Unfortunately, it's a total waste of money, and is useless. Customer support is no help whatsoever.

This is the most portable battery extender I've seen for the iphone and very reasonably priced. It charges the iphone about 70 - 75% from 10% remaining. My favorite part is that I can carry it in my purse and use it for emergencies since it is so light and unobtrusive.

I own both an iPhone 3G and an iPod Classic. While the Classic holds its charge for a long time, the iPhone's battery can be depleted fairly quickly when I'm using it to retrieve email, run applications, and connect to the internet in addition to talking. When I saw this Kensington battery extender, I knew I had to have it.

The battery was larger than I expected, slightly more than one-third of the length of the iPhone itself. In retrospect, that shouldn't have been a surprise, given that it's an extra battery. Once I got over the disconcerting appendage to my iPhone, I found it invaluable. I keep it charged and carry it with me so I can just plug it into the iPhone, with no interruption to service.

You can charge both the battery and the iPhone together, or you may charge the Kensington separately using a USB port. (You cannot recharge the battery via an electrical outlet.) The charging itself takes a few hours to go from empty to full charge -- too long for new technology, in my opinion -- but the charge it delivers to the iPhone or iPod is immediate. You can operate your device directly from the battery power, or, if you aren't using the iPhone/iPod, you can let the Kensington transfer its charge to the main unit. Although it cannot fully charge the iPhone, any extra battery power is welcome.

The Kensington mini-battery is one of those items that you don't know you need until you have it -- and then you cannot imagine how you did without it.

-- Debbie Lee Wesselmann

If you use your iPhone a lot then you need a battery backup device. I purchased a battery backup that requires a USB cable and it works great, but I was looking for a device that was more compact. The Kensington device is handy because it plugs in directly and takes up little space in your pocket or glove compartment. I was able to attach it without having to remove my phone's protective case. The downside is that it will not completely charge your phone if it is very low. It is great for emergencies but not so great for long games or phone calls. I have not used this device on an iPod, I think it would probably work well on one with low power comsumption.

I have never reviewed an Amazon product, though I would never purchase an item without reading them. (I know - duh!) I recently purchased the Kensington unit to go with my newly purchased iPhone 3g. It is so useful I must write! I have used it for several weeks. Although I haven't actually timed it, it seems to charge in about the same time to takes to charge my iPhone. I generally plug it in to the iPhone if the phone is between 10 - 20% charge. Within minutes it is up to 75% charge. (in the time it took to write this review it took my iPhone from about 10% to about 80% charge). And in far less than an hour the phone is fully, or nearly fully charged. I can use the iPhone while it is charging. The fact that the Kensington unit uses a mini USB port for its own charging means that I don't have to have the specialty 3g iPhone cord available in order to charge. My camera cord, my old motorola car charger, many cords at my office or friends house, etc. There is always a mini USB cable and a USB charging source. AND you can charge the Kensington and the iPhone at the same time. My wife has the 1g iPhone (BTW, it's cable will not charge the 3g) and she had to buy and keep charging cables everywhere. Office, purse, night table, etc. I can now use pre-existing usb cables :) Because the 3g can be used for so much,it is in use most of the day, so the battery often won't make it thru the day. I charge them both on the night stand at the same time with a mini usb charger. In the morning the Kensington is small enough I drop in my pocket and head out. Appearance and fit are great, although I would not them plugged together in my pocket. Kensington - you did awesome on this one!