On the status page (or wherever appropriate) list all the connection types (Strava, Garmin, Map My Run, etc.) as well as the number of CS accounts using each connection type. To be more useful, the count should be of all accounts and the number of accounts that have imported runs in the last thirty (or whatever) days. This second number is the number of active accounts.
It might be even cooler to have the number of activities imported in the last thirty days, the average distance of each activity, and the average number of activities per active user.