mainly want to use a BT headset to listen to audio from a pc or a pocket pc device:
*Do all the devices work with computers, or are some only for mobile phones
I don't think transmitting audio from your PC to a Bluetooth headset is any option of any of the Bluetooth supported profiles. Yet.
Audio from Cell Phones...yes. But I don't think you can route your PC's sound to your PCs Bluetooth devise.
I could be totally wrong about this, of course. But I've never found a way to do that.