The Plantronics 510 bluetooth actually works!! I am very happy. This is the 6th or 7th one I have tried, the first one did work and was really tiny and pretty cool, but caused severe ear pain and quit working in 3 months. The others, another plantronic, several motorolas, and a blueant....not good. No one  could hear me or the sound was so uncomfortable("are you in a wind tunnel??") they did not want to continue the conversation. This Plantronics 510 easily switches between between 2 cellphones, and I can be heard outdoors, in the car, while shopping. The buttons are easy to access, the charge lasts all day. It's pretty comfortable, I wish it were a little flexible for a better fit. It's pretty ugly but it works very well.