The easiest way to include it in your WSGI setup is to define it as a filter inside your PasteDeploy configuration file like this:
[filter:statusmessage]
use = egg:qc.statusmessage#middleware
cookie_name = status
[pipeline:main]
pipeline =
...
statusmessage
...
myapp
Right now there is only the cookie_name configuration parameter which lets you define the name of the cookie to use for storing status messages across requests.