I think the Windows event log works like this. Sadly it's very opaque and difficult to use for non admin apps (you need admin rights to install your logs for the first time. Afterwards you can run with less privileges.)
Originally there was only one system-wide application event log and you needed to be admin to install your message definitions but it all changed in Vista (IIRC). I'd lost interest by then so I don't know how it works now. I do know that the event log viewer is orders of magnitude slower than it was before the refit.
ETW is for high speed general purpose logging of low-level events with multiple collection mechanisms including realtime capture.