FOR WHAT IT'S WORTH....Possible alternate fix. My 08 hardware XR, like many others, has been very bad connecting to to my iPhone since I first got it. It disconnects continually while I am riding, making it almost useless. As I have said many times, my first XR, an 06 model, has worked flawlessly from day one.
So, recently I change my tire to a treaded Burris. Now, here is where it gets very unclear about what fixed my problem. I was very careful with removal of the Vega tire, and the wires that needed disconnecting, etc. I had heard some horror stories from a few whose boards did not work right after changing their tires. I cleaned everything as I went along. While I had the board all apart, I decided to install my brand new aluminum flight guard plates, as I was putting everything back together (previously had float plates on). The board works fine....plus... as long as I am right by the board or riding it, now my iPhone AND Apple Watch stay connected!!!! I have ridden it at least 4 times since the tire change, and it seems to be consistently working.
I have 2 theories: 1) in disconnecting and reconnecting the cables, (which were a bit difficult to remove, but snap locked into place when reattached), I corrected a poor connection to the control board, which allowed a stronger bluetooth signal. 2) the new flight guards, from flight fins, being metal (heavy gauge aluminum) are reflecting the bluetooth signal and acting like an analog amplifier.
I am not sure which is the case, but my guess is that number 2 is the most likely reason.