DTrace on FreeBSD?:

"I'm happy to now report that Devon O'Dell has started working on a port to one such system, FreeBSD. This has been talked about before (in some cases, with braggadocio), but Devon is the first to start the work in earnest. And indeed, work it will be: DTrace isn't a simple system, and it has several dependencies on other, Solaris-specific system components."

(Via The Observation Deck.)