The standard Bluetooth Icon that most people can recognize is:

Bluetooth logo

Apple has a slight variation on it, but it is about that same. The B look:

Bluetooth Mac Icon

So why does my navigation system show a totally weird Bluetooth icon? You see, it has a three blue circles on top of a BT. Weird!

Lexus Phone Bluetooth Icon

BTW, I love the bluetooth connection feature in the nav. I use it all the time. I hear the next iPhone will support bluetooth stream of the iPod, which would be nice as well for driving.