Auto-connect bluetooth device to iPhone


I am working on a project where I need to be able to detect if my phone is in range. I have managed to get a WiFi sniffer working, and my iPhone sends WiFi packages every few minutes when it's locked. However, I want the detection to occur almost instantly, with detection rates being somewhat like every 1000ms.
I think the best way to accomplish this is over bluetooth. I have tried using HM-10, but it will only connect using an app. The phone should be detected while it's in my pocket, with no user input needed. Once a device was paired, the iPhone should automatically connect to it.
I have been searching google for the past few hours to no avail. Somehow it has to be possible. My bluetooth speakers and my car also automatically connect to my phone while it is in my pocket, so there has to be a way.

Maybe one of you guys knows of a bluetooth module or a way to solve this problem?