Cardhop can integrate with Fantastical to quickly invite a contact or group to a calendar event.
To use Cardhop and Fantastical together like this, simply type 'invite' or 'fantastical' into Cardhop followed by the name of a contact or group. Use the arrow keys to select the email address you want to use for the invite and then hit return.
You'll then be taken to Fantastical and a new event creation window will appear, with your chosen contact(s) automatically added to Fantastical's Add Invitees section. Type any remaining event details into Fantastical's natural language parser and hit return to create the event and send the invite.