A legitimate use for the DM-50 hot-shoe mic
 

I've gone on record saying that I couldn't see a need for using the little Canon DM-50 hot-shoe mic on the XL2, but it looks like I'll have to eat my words now.

If you're in a situation where you don't need the EVF assembly on the camera and you still need to take audio from the camera for some reason, the DM-50 is a nice solution. For example, you might have the XL2 mounted on a crane. Or you might be using a stabilizer such as a Glidecam or a Hollywood Lite Running Rig. In these configurations, in order to save weight you generally won't put the EVF on the camera, since there's already a monitor mounted on the stabilizer system. Usually you won't bother with audio on the camera with that type of rig, but if you need it, you can attach the DM-50 to the Advanced Accessory Shoe and there you go.

It's about $180 USD and provides stereo audio with a couple of different pickup patterns.