I've created a tool called procurve-watch. It creates a backup of the running switch configuration through secure shell (using scp).
It also diffs backed up configurations against older versions, in order to keep track of changes. If you run the script from cron every hour or so, you will be notified by email of any (running) configuration changes.
The tool can backup hundreds of switches in seconds as it is running the configuration copy in parallel.
A tool like Rancid may actually be the best choice for this task, but it didn't work. The latest version of Rancid doesn't support HP Procurve switches (yet) and older versions created backups containing garbled characters.
I've released it on github, check it out and let me know if it works for you and you have suggestions to improve it further.