I have a dashcam in my 500. It would work well in a 500L as well - it is this one:

http://www.amazon.com/gp/product/B00NIDPJ8O/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

It's not rearview mirror, but fits discreetly behind the mirror for me. Comes highly recommended on dashcamtalk.com.

It is my second dashcam. I too wanted rearview mirror mount, but most of those have severe limitations, such as they're either "clip-on" or lack in features/quality.

Good luck - definitely check the forum I suggested.

 

Aelfwyne, thanks for the tip. I like the model that you used in your 500, but will have to carefully check measurements as the 500L has a wide rear view mirror mount which may not have enough space to mount the dashcam behind it and still have a clear shot of the windshield.

 

I have two soon to be three dash cams. I run them in all my vehicles. I wanted a cheap camera but didn't want to give up quality. You do get what you pay for.
The one I have are full 1080P and high def audio.

I have the Hawkeye

http://www.canadadashcam.com/

It comes with a suction cup or for $15.00 you can get a rear view mount.
http://www.canadadashcam.com/collections/windshield-mount/products/rear-view-mirror-mount


The one in my daughters Fiat Sport I have suction cupped right beside (passenger side) of the rear view mirror. It has never fallen off and when I tried to remove it one time had a heck of a time pulling it off. It's a good set up.
I am using a 32Gig memory card (he sells them as well) and have it set up starting a new file every 3 minutes. Makes it really easy to find something with out looking through hours of recording. The camera will loop it's self once the card is full so just set it and forget it until you need coverage off of it. Should you be in an accident the camera has a g sensor in it so will protect that file from being copied over.
They also have hard wire kits that I highly recommend. Hook it into a ignition source so it turns on and off with your key. He uses a Tap a Fuse set up so you can tap into any circuit in the car. I tap into my cigarette lighter fuse.
http://www.canadadashcam.com/collections/hardwire-installation-kits


Here are some sample videos of the Hawkeye and features below...(make sure you click the gear on the bottom right side of the Youtube window and change to High Def.)
http://www.canadadashcam.com/pages/videosample

Jason at Canada Dash cam has fantastic customer service. I highly recommend him.

 

Does the hawkeye screen turn off during driving? Can you set it so it never turns on?

 

I have the E-Prance Mini 0803 mounted in my 500E. Hidden behind the rear view so it's pretty inconspicuous to other drivers. I use it in two cars sometimes so I have a mount in both cars. It's fairly cheap, buggy sometimes but it does the job. The forum that another poster suggested is a pretty good one with lots of people with their inputs on various dashcams.

Here is sample shot from mine.