The piwik documentation noted:
Some Piwik users automatically provide their CMS customers with Piwik statistics. If you want to provide a one-click automatic login to Piwik for your users, you can pass their login & the md5 string of their password in the URL parameters:
This will log the user (create a cookie in their browser) and redirect to the index.php on succesful login. We advise to do this authentication over HTTPS. Note that this authentication method doesn’t work for the Super User.
You can also specify the URL to redirect after a successful login, if different from the default Piwik dashboard page:
However, I am having problems getting the default dashboard that is loaded after logging in, be for a specific SiteID. I’ve tried a variety of variations with the url= parameter in the URL string, and just haven’t been able to make it work. Maybe I’m missing something though, any help is appreciated.