SD Card Recovery is a file recovery application for the Mac. It allows you to scan your drives for files that may have been deleted in the past. Some of those files are recoverable even after you have emptied the trash. Of course, the app supports SD memory cards, but you can also use it with USB flash drives and hard drives. When I tested it, every drive connected to my Mac was available (with the exception of the my Mac's internal hard drives).
To start a scan, all you have to do is select one of the drives and then select what types of files you want to search for. There are profiles for some cameras (which include filetypes used by them), but you can choose a format or scan for them all. There are image formats and video images available. After you do that, the scan will begin and the results will appear at the top-right pane. Below that, you will find a preview of the found images.
In my testing, the app found some images on a USB drive. Some of the images that it found were still on the drive; in other words, they hadn't been deleted. This made browsing through results a little harder.
