General :: Backup Only The Files Which Have Changed?

if there an application which does the following:

1. I have a laptop with an internal 200GB HD.

2. I run the application & it creates a list of all files (size & time-stamp) without actually storing them. Let's call this the "snapshot list".

3. I update some of the files on the laptop.

4. Now I run the application & it only copies the files which have changed on the laptop, that have different size/time-stamp from the snapshot list, onto some external media, such as a memory card. Of course, the files should be copied onto their proper location in the directory tree & not just pile up in one place.

Why is this useful? although the laptop has a 200GB HD I typically only update a small number of files, whose total size is maybe 10MB or so. If I could only backup those which have changed, I could do this with a tiny SD card instead of lugging around an external usb HD.