reh,
Using the compass is going to be very laggy. You can compensate for the latency with clever use of the rotational accelerometers. However, you are going to be surprised by how bad the result will look compared to marker tracking.

QCAR has been out of beta for a while now.

If you want to move the camera off the marker, it is best to use another marker to pick up the tracking again. But you have to bring the markers into a unified coordinate system. Which is exactly what my project is about:
http://ar.qualcomm.at/node/2001030
Have a look at it. I think it will suit your needs just fine.

You have control of what happens when tracking is lost and found. See the TrackableEventHandler script that comes with the samples. You could choose not to hide the renderers when tracking is lost. You could also "unbind" content from a trackable at any time by unparenting the content from the trackable (set the transform's parent to null). If you do this you may want to set the World Center Mode on the ARCamera to NONE, which guarantees that the camera will not move in the scene.

- Kim

I'm also interested in this "persistent behavior" of objects around the camera space. Anyone can say more about this compass? Or point me to another forum topic with some examples? Thanks!

What compass? Unity or Qualcomm function?
I seem to recall that in the ARcamera in Beta, there was persistent targeting in the pose functions. Is this gone now in 1.0?

You can accomplish some of what you're looking for by using the compass, but it's not going to be as precise as the image registration that QCAR provides.

For instance, if you want to retain that particle animation, simply don't disable its rendering when tracking is lost (e.g. OnTrackingLost() in the samples). Then orient the field according to the compass heading until the image target is in view again.