Sure and sorry to bother with I know this is an old post but a really useful, I’m building two devices that when I press the button will alert the police https://www.youtube.com/watch?v=mXAdaPBmKQQ
and I noticed most new bluetooth Selfie buttons are not working with any of these techniques, the only one working is the one from the Amazon link also I noticed when using this command sudo showkey nothing happen when I press the already paired AB Shutter3 but that is not the case with the one from the Amazon link,