Server permissions of an activation stored procedure of a Server Broker queue
See Signing an activated procedure for an example of how to properly sign an activated procedure exactly so it it can leverage VIEW SERVER STATE privilege from an activated procedure. The steps are:


inspect the procedure code to ensure that you trust it
change the procedure to have an EXECUTE AS OWNER clause (without EXECUTE AS, even if the module is signed, the principal will not have access outside the host database because of how Service Broker executes the activation procedure)
create a certificate with a private key in your app database
sign the procedure with the private key of the certificate you created
drop the private key of the certificate (to prevent it from ever being used again)
copy the certificate into the master database
create a login from the certificate
grant AUTHENTICATE SERVER to the certificate derived login
grant any additional privilege required by the procedure (e.g. VIEW SERVER STATE) to the certificate derived login