Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Useless for iPhone 3GS

Upon plugging this charger into my iPhone 3GS and my car power socket, I received a warning message on my phone which told me that the device is not compatible with the phone. So, the device was basically useless. I wonder if it actually works with iPhone 3G or iPhone 4? The packaging says nothing about the device being made for iPhone 4. My recommendation is stay away from this product. In the end, I went to the Apple store and bought something that I KNEW would work!