This is a really interesting idea, but right now we don't have any way to limit bandwidth usage.
You can see bandwidth and storage usage in the Usage Reports tab in the panel. It isn't fine-grained enough to see individual object bandwidth though.
We are introducing usage notifications in the panel soon. This feature will allow you to create notifications when your account reaches configurable levels of bandwidth, storage or dollar amounts.
We'll do some thinking on this and look at adding something along these lines in a future release.