Just want to subscribe to this feature request. Same for me: when my car connects, Poweramp should start playing, but when I connect my hands-free headset in my office, I don't want to continue listening music (on one ear only 😉 ).
As output devices are already shown in Poweramp's output chain, it would be great to have a list of seen (bluetooth) devices to check/uncheck below "Resume On Bluetooth" option.