Do I need to mess around with the user-agent, or is there a less intrusive 'hack'?
Hope this helps.
You have multiple options available:
2000's mobile (WAP style)
Ready to use, just go to https://calendar.google.com/calendar/m
Edit 2022: Seems to no longer be available and redirects to /gp
2010's mobile (iPhone 3 style)
Ready to use, just go to https://calendar.google.com/calendar/gp
Use this url to configure the widget: https://calendar.google.com/calendar/embedhelper
Then you can use the iframe code to integrate this.
You may also want to just extract the
src value and HTML entity decode it to use in your browser (Decoder: https://mothereff.in/html-entities)