Bluetooth connectivity is designed for app usage on your iPhone or Android to allow volume and other adjustments directly to the hearing device. iPhones allow for direct streaming of phone calls, music and iBooks directly to BOTH aids while most of the Android phones require an accessory to accept the signal and send it to the hearing devices.

Oticon Hearing Aids
Signia Hearing Aids
Resound - Rediscover Hearing Aids
Phonak - Life is On Hearing Aids
Starkey Hearing Aids