How do I know the appointment details in an iframe parent window

Hi. I'm using the booking page in an iframe in my web chat APP. If customer successfully booked a meeting, after the iframe is closed, I want to send some message to the visitor in the APP like "Your successfully booked the meeting with agent xxxx. The start time is: xxxx. Location is xxxxxx." 

But how can I get those info from the iframe after booking is done? Is there any notification that can be sent to the iframe parent window, so that my APP can know the booking status and details? 

In Calendly, they have a notification to parent window feature when used in an iframe. Does Bookings has a similar feature like this?

https://developer.calendly.com/api-docs/ZG9jOjI3ODM2MTAz-notifying-the-parent-window