Windows application to detect running apps based on events

No.. better use windows service only.

Cant we do it with WPF

Windows service should be the preferred choice. you cna refer these microsoft tutorials to use windows api

https://docs.microsoft.com/en-us/dotnet/api/system.diagnostics.process.getprocesses?view=netframework-4.8

https://docs.microsoft.com/en-us/windows/win32/wmisdk/wmi-tasks--processes

Create windows services,

and below link may help you.

https://stackoverflow.com/questions/842533/in-c-sharp-how-do-i-query-the-list-of-running-services-on-a-windows-server