Unsubscribe a user from activity feed, if his access-token is revoked?

[thk]

Current situation:

1) Bob (id 123) connects via a client to his fitbit-account

1.1) and subscribes for the activities-feed.

2) Joe (id 124) connects via a client to Bobs fitbit-account (he knows his credentials for whatever reason - could also be Bobs second account)

2.1) Bob's access-token is revoked

2.2) Joe cannot subscribe to the activities feed, because Bob (subscriptionId 123) is still subscribed. Error 409 

2.3) Bob cannot unsubscribe from the feed, because his stored access-token is invalid

Is it possible to automatically unsubscribe Bob from the activities-feed, if his access-token and refresh-token is renewed?

[thk]

The best solution i found is, to tell the second user to revoke the access for the client application on fitbit.com an reconnect afterwards again.