Widgets are full screen pages that can be embedded into the main page loop or the page loop of an activity.
I might be reading this wrong, but this sounds like it should be possible to access the widget during an activity. I made a quick test widget that referenced the Activity object, and was able to display times, distances etc on the simulator. However, when I deployed it to my 920XT, the widget only appeared under the main page loop, with 0.000000 elapsed time and null distance, and was not available during an activity.
Am I misinterpreting the documentation, or is it somehow possible to add widgets to the activity page loop?