I did try this when I first got the bike. I connected the bike to my iPhone, then to my Sena helmet headset. I did like the ability to control the volume and skip tracks using the controls on the bike (I can do the same things on the Sena control module but it's a little more awkward). I also liked seeing the track name on the center display. But I realized that this method did not allow me to use the phone function if I needed to--I think it just treats the phone as a music player. I only rarely make phone calls from the bike (and only when stopped) but I sometimes need to answer calls when riding. To do that I would need to unpair the phone from the bike and reconnect it (wirelessly) to the helmet. It's simpler to leave the bike out of it and just have the phone talk right to the helmet.
I also wonder if going through the bike would pass through the turn-by-turn directions from the Map (or Google Map) app in the phone into the headset, so I can get spoken directions. I need to try that, I guess.
I thought I might be using the built-in speakers in the bike but playing loud music while riding kind of makes me feel like a jerk. I used to do it all the time on the Gold Wing, but I was a lot younger and not so aware of people's annoyance at bikers who do that. I did load up a flash drive with some music and tried playing that through the speakers; it works fine. I still might use that sometimes.
Interesting that all of the gosh-wow features of the Deluxe model (Bluetooth, auto-cancel turn signals, speakers) are not as useful as I thought they would be. I think the ABS and traction control, though not as visible or "sexy", might be the only features I'll really end up using.