I am new to Mac desktop app development, but i have good experience on programming iOS apps...I have been looking for the solution for the following development tasks for a Mac desktop plugin app, but couldn't find the right answers yet. Could someone please guide me thru to get it?

I want to develop a plugin app for iCal application, and have a custom menu item in iCal app. Is it possible to develop a plugin for iCal desktop app and how to add a custom menu item into iCal app menu? Plugin-> It can be just a .bundle file and can be installed on Mac desktop. It can have notification or IPC mechanisms between this plugin and iCal app.
I want to sync the calendar events between iCal and my server through my plugin. How is the feasibility for this task and do it?
Please help!

Thank you.