I have the bluetooth Ultra-Gauge and use it with my iPhone. So far, so good. I also have an Intravee and have it feeding system information to the nav screen while driving down the road and listening to tunes on the iPod. The Ultra-Gauge shows the coolant temperature 1 to 2 degrees F higher than what the Intravee is collecting and putting up on the nav screen. Anybody have a guess why there would be a difference since the information feed is coming from the same internal car network (Can-Bus)?