Summary Cards are really helpful in dashboards to spotlight information, and of course record selectors help in a number of key ways. There are two areas that would elevate these to encompass more uses to make dashboards more customizable. First, an ability to pull additional information outside of just metrics in a summary card (i.e. text from formulas). Second, like the record details widget, it would be helpful if the summary card could use a record selector without having to link to another record.