Hey Sunny,
The rate limits are imposed on a per API key basis (or single token if you’re using OAuth) so this means it’s applicable to each individual account.
As for checking remaining calls, we do not currently have any plans to expose how many are left in the response headers however I can see that will be very useful for devs to base their requests around. I’ll see if we can introduce this on release.
Also it’s worth noting, I’ve posted an update on changes to the introduction date of the API rate limits here.