Hello - does anyone know how to write up a suitelet with iframe? We're looking to display some data in NetSuite from an external BI application.

You can add a html field like that:

form.addField({
                id: 'custpage_htmlfield',
                type: serverWidget.FieldType.INLINEHTML
                });

            scriptLoad.defaultValue = '<iframe> </iframe>';

I'll give that a try - thanks!