This... probably isn't the answer to your problem, but...
I use MS SyncToy to back up files to the phone. It has three basic sync modes. I've set up a number of pairs including a selective back up of the phone system as suggested here. This program can be automated by task scheduler. I use USB mode, but I think I've successfully tested with WiFi File Sharing.
Depending on how data is stored in the calendar, contacts app, etc., it may be theorectically possible to sync specific folder pairs that contain the relevant data. However, this would require developer mode to access the full file system. Even if that works, I'd be surprised if data in a desktop program was stored in the same format as on webOS, though these days it might be possible. Failing that, you'd need some kind of conversion program. I assume palm desktop was built to offer data to hotsync in a form simplified for the handheld. With webOS being a Linux based system, it might be simple to sync to a Linux desktop (big maybe) or even a MAC or Windows system if common formats are used (unlikely?). Of course, outside of Windows you'd need other sync programs.
1. (Common type) File sync & transfer = Easy
2. WebOS system access for the sync program = Possible with Dev mode?
3. File type compatibility = ? I expect unlikely.
4. Data conversion options? I have no idea, but there exists the Data Transfer Assistant which offers a one time, one way conversion and transfer service from Palm Desktop & I think Outlook. If the code can be examined (Is it OSS?) it might be possible to work the same process in reverse, giving two way conversion prior to synchronisation.
That's it. Optimistically, a developer who knows webOS might read this and confirm it's possible to do all this with a script or batch file to run exisitng tools. Or maybe someone could write or adapt a program to perform conversion if the data files are not compatible.
Or maybe not!