Where in Salesforce is the “Keep me updated on this action” field stored?

I have the following field displayed on my Actions form:

Keep me updated on this action

However, I can't find any field in Salesforce where that might be stored.  What's the deal?

Great question!  At this time that field is not currently stored to Salesforce.  The intention is that this will get saved to Salesforce with a future release of the Actions Salesforce package.  But at this time, it is not.