First, sync Palm with Palm Desktop.
Next, open Palm Desktop, select the Calendar view, navigate to File | Export, select Export Type as Date Book Archive, Range as All and provide a file name. This will export the calendar data as Date Book Archive (.dba).
There's a paid tool called DBA2CSV that converts .dba files to .csv files. However this can be done for free using Yahoo Calendar. Login into Yahoo Calendar and via Settings/Import, import the .dba file. It helps to have an empty Yahoo Calendar. Via Settings/Export, export the calendar as .csv file.
Login to Google Calendar (also works with Google Apps For Your Domain GAFYD Calendar) and import the .csv file into any of the calendars. It is a good idea to create a test calendar and test the import before importing into your real calendar. That way if anything goes wrong, you can delete the test calendar.
Seems like a lot of steps but it's a pretty smooth and free migration, after which you have a calendar that's accessible on the cloud and on the iPhone, with the iPhone's builtin alert mechanisms. If you have any difficulty with any step, post a comment.