Recommend a web-based caldav client
Achim J. Latz commented
Webical has a caldav plugin that seems to work, at least in their demo: http://code.google.com/p/webical/
The demo is located here: http://demo.webical.org/
You can see (after logging in) that the calendar type is caldav:
Maybe hack a CalDAV backend for http://monket.net/wiki-v2/Monket_Calendar
Be sure also that google mail could load a remote calendar.
I've try it but without success