When building your app, there are some considerations to keep in mind:
You will need to have a web app that can be displayed inside of an iframe because HubSpot will not process any content of the iframe, so you can't set the iframe URL to a backend SIP service.
The height and width parameters set through the settings API will determine the size of the iframe. Windows with a height of 600px and a width of 400px work best for the widest range of browser window sizes, including smaller screens.
You should make sure that error conditions appear inside the iframe. This is so your app can alert users about audio issues, network problems, or other errors.
that's not my point! How to show the content of the iframe? Simple example: an index.htm at my webspace, the index.htm outputs "Hello World". How can I show "Hello World" inside the iframe? It seems not possible 🙂