SQL Express : How to detect if Express is installed?

I recently stumbled across this question from a customer : how can you detect if SQL Express is installed on a local/remote box?

Apparantly, the Add/Remove Programs list lists some confusing entries including general "SQL Server" et all, so how do you know if SQL Express is on the box or not? Here's a trick that I learned from Mike Walach, PM and great guy on the SQL Server Express team : enter the world of the wonderful SQL WMI Provider. Mike posted a cool piece of C# sample code on his blog here: https://blogs.msdn.com/sqlexpress/archive/2006/07/29/faq-detecting-sql-server-2005-using-wmi.aspx