Please don't forget the Android users. With Bluetooth or micro-usb (with an iPhone adapter), it would then be a software issue to support both rather than a hardware issue. While I don't have empirical evidence to back this up, my feeling is that Android devices may be slightly more popular for Diabetics because they are generally more budget friendly than an iPhone and diabetics have enough costs in their life already (my wife is Type 1.)

Regardless, please consider support both eco-systems.