I tried this, it works nicely, saving screenshots under the project, into the specified folder structure when testing with Unity Remote with an Android device connected and on PC.
Could not get it to work when built to device. I changed the path to the sdcard and also to phone, tried using / and \ between the folder names, but could not get it to save any images onto device.
The app did pause for a moment when it should have taken the shots, so I guess it did, just could not write/save them for some reason.
Does the app have to have some rights set, so it can write to those image folders?
Well, anyway I don't think I'll be using this, just tested.
Br,
szomaza