Have you seen the details on the Blueborne attack?
Any device unless patched can simply be taken over via bluetooth by just being in range of a hacker!
If someone places a bot to hack all devices in range automatically in a subway station, they can get thousands of devices taken over and have a huge bot army.
This is one of the bugs, which renders all unpatched devices to be no longer used. So any Android and Windows without security patch installed, and iOS before version 10 should no longer be used. And for Android it's unlikely, that your phone has currently the September security patch installed, if it's available for your phone at all!
Another solution is to disable bluetooth on all devices.