Fine, not exactly as advertised,
Verified Purchase(What is this?)
This review is from: LUPO USB 'Bullit' Car Charger for iPhone 3G/3GS/4 iPod Touch Nano Classic Shuffle - BLACK (Electronics)
Although the specs say 800mA, the unit I received says it only outputs 500mA. That's probably just about enough to charge your phone when it's not in use, but if you want to use this with your iPhone in sat nav mode (i.e. with Google Maps) you'll find that it's not capable of charging the phone, merely slowing the rate at which the battery runs down. Useful to an extent, but you still wouldn't have much of a chance of getting from, say London to Edinburgh using your phone as sat nav and still have any charge left at the end.
The tell-tale that this isn't quite up to scratch is to check a standard Apple mains adapter, which outputs 5V==1A. I'll keep this as it might come in handy one day, but I'll be looking for a 1A adapter for my car, too. The lack of power may explain why I and at least one other reviewer constantly get the 'Charging is not supported, etc.' error when using this adapter.