I have the SPH10, and the straps on the helmet make it aggravatingly difficult, at times, to hit the phone button, especially when wearing heavier gloves in colder weather. Additionlally, I will occasionally get a false phone button hit/activation by the strap (this sometimes occurs as a result of normal head movement to check traffic, or, just stretching the old bones and muscles).
Recommend that a wireless remote button on the handlebars be considered, or, better yet, a voice activated command/control function. This would allow the rider to safely (left hand not leaving the handlebars), with more positive control, make desired selections, whether it's adjusting volume, activating intercom, or initiating the phone. If this option were available, it could be sut up as a user option, giving the user the choice to use the normal headset controls, or, deactivate them, and use the remote wireless controls on the handlebars, or, my prefered method, use the voice activated command/controls.
I personally have no issues releasing the left hand from the handlebars, but, some riders (especially new, in-experienced riders), might/could (myself included, in some scenarios), find themselves in a dangerous situation with their left hand up by their headset controls, especially if caught in a sudden emergency situation (road hazard, animal crossing the road, sudden cross wind, abrupt uneven road surface, erratic/all over the road vehicles, etc.). With a voice activated command/control function, the rider would be truely and totally "Hands Free" for all functions while riding their motorcyle.
Don't misunderstand me, I love the product, but think this added option would be used by many, if available. At some point in the future, some states, for safety reasons mentioned above, may require it? Look at what most states are now requiring in regards to cell phone use while driving.