You might want to look into setting up a RAID1, RAID01 or RAID10 array of drives. Most Motherboards have up to 6 SATA slots for setting up various configurations of RAID. You would probably interested in any of the RAID mirroring options. It's like an instant back up of all things instead of relaying on a schedule or you…
Why do you need to backup apps and OS? Leave that alone, and back up the profile (emails and such) and your files. An awesome backup solution would be backing up to a raid1 array, as backups can fail. You CAN install the OS and all your apps 100% before you started mucking with shit, then make an image and back that image…