Proximity BLE Chat (PBLEC)
Intro
My interest in BLE began when I unsuccessfully tried to create a camera shutter app for my Garmin watch. There are no dedicated system APIs on iOS for this. Selfie sticks solve the problem with a hack. They pair as HID devices, keyboards in particular. The volume button in most camera apps acts as a shutter, including the native iOS camera app. When you use a selfie stick or something similar, its essentially a keyboard with only one key for volume that triggers capture.
Garmin SDK does not allow connection as a secondary peripheral or setting the right HID profile. There are, of course, solutions that try to solve this using a companion app, which needs to be installed beforehand on both the Garmin watch and the phone. Garmin itself could probably do this using private APIs.