When you add a picklist value to the Fastcall widget you will see it along with call results, subject, notes, etc. Any Task picklist can be added, but must be a picklist. If you have a custom radio button on your Salesforce Task, for example, you can change this to a true / false picklist. There is also an option to add a follow-up call to the widget. This creates a future open task, for example “call in one week.”
FastCall Task Picklist