For some. the best choice will be to simply upgrade the operating system itself, since Windows 7 includes a simple to use local backup utility and already automates most of the things that tune-up did in OneCare, such as defragmentation.
http://www.petri.co.il/windows-7-backup-restore.htmPrinting, WiFi setup and other core system operations have also been improved, so most users will get far more out of the os upgrade than trying to "patch" Windows XP with add-ons, especially at a list price of only $120 for the upgrade. However, those without the minimum 1GHz Processor, 1GB RAM and 20GB drive space available may have to consider other options.
The monitoring abilites in OneCare worked by phoning home to the central servers to keep their status current, where the hub could then collect that status when it connected. Since this required an authentication system, which Windows Live provided as part of the billing and telemetry system, it would likely be cost prohibitive on its own. For this reason, I don't expect that there are many other systems like it out there except those designed for business systems with central management.
Rob