Ubuntu :: Remove Old Backups Based On Total Size, Not Just Backup Age?

I'm looking for a standalone backup manager with the following properties:

1) Easy scheduling.

2) Automatic encryption of backups

3) Ability to remove old backups based on total size, not just backup age. (to avoid overfilling backup media)

4) Since this is going onto a business-critical machine used by a techno-peasant, it needs to have a snazzy, graphical interface for easy monitoring and configuration.

I am sure I *could* write this myself, but I find it hard to believe that there isn't one out there already, and I am lazy. Unfortunately, there are also a very large number of backup programs out there with less than complete descriptions and I am getting tired of installing each in turn to see what it does.Has anyone stumbled across something like what I just described?