Neat idea, but probably not practical.
You'd have to have widgets written so they could accept a "refresh now" signal from another arbitrary app, then your hypothetical app would have to be aware of the API for all the apps on your screen.
If Google standardized interprocess communications and had a standard API, it would likely be the subject of many security bulletins for quite a few versions.
If all of your widgets are from a single developer it might be feasible.
Sent from my Nexus 7 using Android Central Forums