Vacuum

I'm sat at the Haskell Hackathon, and dons is doing a demonstration of  
a tool called vacuum which can observe the state of ghc's heap while a  
program is running, in various states of evaluation.  I'm getting  
pretty excited that this could be used to generate a hat trace using  
ghc-api, rather than hat-trans.

I wanted to check if anyone had looked at the API this is using or  
not, and if anyone knows of any immediate trip-wires that I might  
encounter thinking about this.

Bob