The idea is to create a new widget or make an enhancement to an existing widget to display a count of the distinct/unique values in a field.
The basic indicator widget allows you to display a total count of records, or statistics such as minimum, maximum, average etc. But currently not the ability to display the count of unique values.
e.g. given the following values in a hypothetical field 'FirstName':
The count of unique values would be 3, for 'Paul', 'John' and 'Fred'.
Ironically, when you try to set a filter on the basic 'Indicator' widget where the value is equal to something, the widget provides a drop down list of all available distinct values - so it is likely already performing the necessary query! All we need if for it to do this and return the count of those as the actual result of the widget.