Backups are incremental, in that only the data that actually has changed is overwritten. Your backups are located here:
* Mac: ~/Library/Application Support/MobileSync/Backup/
* Windows XP: \Documents and Settings\(username)\Application Data\Apple Computer\MobileSync\Backup\
* Windows Vista: \Users\(username)\AppData\Roaming\Apple Computer\MobileSync\Backup\
You would have to contact the app developer to see how to listen to these files on your computer. My guess is that you can't, but that's an educated guess. Given the backup file structure, it's doubtful you'd be able to extract the files from it.