Off hand, I don't know of any GUI tools for this purpose, but that is not to say that they don't exist. If you are looking for a project to start learning about GUI programming, this might not be a bad choice of application. As I see it, you will be focusing on the GUI portion while interfacing to underlying shell system using the existing backup command line tools. As such, you won't have to worry about the mechanics of the backup mechanism. Such a design would be in keeping with the Unix and Linux programming philosophy (read the free book The Art of Unix Programming for more on this subject).
In order to start, you will need to pick your development platform. The easiest way to go will depend on your choice of desktop environment, which I assume will either be Gnomoe or KDE. Under Gnome, you can develop using the GTK++ libraries. The modern way is to use a form builder that specifies the form in XML and then loads this into your application. Last time I worked with KDE, the tool of choice was Kdevelop and it used QT for its widget library (I'm not sure if this is still the case). There will be a lot of learning associated with this step but afterwards, you can then interface to the underlying shell using the functions available in whatever language you choose to "execute" the command line functions.