Activity distance totals- how to access

I'm a total Connect IQ noob, but have been puzzling how I might create an app (ideally a widget) that needs (among other things) to display a total of accumulated distances from running activities over a period of time (as distinct from the daily 'active' distance provided by ActivityMonitor). I gather that FIT files generated during an activity are themselves unreadable by IQ apps, so I'm wondering how this might be achieved. The native app I have on my Forerunner 235 shows the history totals for week/months etc, so I know the information is available but I can't find where/how I can read this for myself within my own app.    

I'd be grateful for any guidance/pointers, etc

Many thanks

David