Keep in mind that there are two mechanisms here. Headset/Handsfree and A2DP. The former is designed for two way comm as in a phone connection. The second is the stereo one way, and some control in the other (skip, FF,etc). In a device that supports both, the standard is that they are mutually exclusive. If you are listening to music, audio books, etc., over A2DP and a call comes in, the regular audio is stopped to allow two way comm over the H/H profile. Once the call is over, you shift back to the A2DP, regular Advanced Audio Distribution Profile.
Those hacks that have routed regular audio over the H/H profile for devices that had no A2DP capability, typically messed with the phone function because you were sort of tricking the BT system to think it was already in a call.
If the Black Jack has the A2DP profile, I would recommend finding a headset that supports both A2DP and H/H. You will be pleased with the result. Trying to do it all with a BT headset that only supports H/H, while not impossible, won't be very satisfying.
BTW, using just a H/H headset with a non-phone PPC is actually not bad. The Dell X50 supported that and it worked fairly well, but you were not interfering with the phone functionality. It essentially just routed the crummy speaker and mic to your BT headset crummy speaker and mic.
MS-MVP, Mobile Devices
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