Linking cards to Google Calendar is also a phenomenal idea. Another great feature when it comes to Google Calendar is a one way sync. So instead of having to link a certian card to it’s Google Event you could add a date with or without a time to a card and it gets added to Google Calendar automatically.
This would be extremly useful for the following usecase:
I often do weekly reviews where I anwer myself questions and basically identify the good and bad things of the passed week. So I could setup a card with a template and set it as a recurring event. That would require an additional feature that would allow users to set a card as recurring. Google would then remind me of having to do my weekly review and supernotes would have the template ready.