Catch 'Em All allows you to save files to your SD card which are shared via the share menu.
Instructions (are also in the app with pictures):
To be able to save your files in any folder on your SD card you have to enable an option in the File Picker App:
Open the settings screen via the overflow menu
Enable the option "Display advanced devices"
You're done!
The next time you want to save a file to your SD card just choose the "Save with Catch 'Em All" entry in the share menu
Catch 'Em All allows you to save shared files to your SD card