Script for adding the most recently modified shapefile in directory/.gdb to an .mxd

I am trying to write a script that walks through a folder to identify the most recently modified shapefile/feature and then adds that shapefile/feature to the current .mxd. I've seen a lot of diffierent approaches to this on the web (os.walk, os.stat, os.path.getmtime, etc...), but none that quite fit what I'm trying to acomplish. Does anyone know what the would be the module or combination of modules to use?

Thanks,

Pete