You can usually have a bluetooth paired with multiple phones, but if you are looking to have it active on both devices at the same time, I am not sure that you can do that. On others that I have had, you can only have it active and use it on one phone at a time...
I've read that some will be active with 2 phones, the main phone is controlled (you can activate calls) and you can only answer incoming on the second phone. I have not found anything on the Jawbone that states it can do such a thing. I primarily use my Blackberry at work but would like to be able to answer my personal phone for family type stuff. I work often in a noisy server room and have heard good things about the jawbone noise reduction. That's why I ask.
