Among the current cameras with GPS you will notice that more than half also record orientation. Just look at the row towards the bottom of the table that says GPS at the above link.

Now, I have no idea if they use accelerometer or gyroscopes but all those record the orientation of the camera. At least the Casio H20G, which is also among the digital cameras to include a built-in GPS with orientation, is known to use accelerometers because it actually tracks your position indoors (or other places where GPS do not reach) too by measuring direction and speed from the last known GPS location. They call this Hybrid GPS.

How common is it for cameras to have a gyroscope?
In the Google Universal Analytics doc, they show a parameter called Campaign ID. The problem is that there is no other information about the use and the interest of this parameter. Indeed, all other campaign related parameters are very usual (utm_...) but the Campaign ID seems very odd.

Can anyone provide more insight about it, please?
