I just finished a preliminary version of a very simple visualiser of finite pi-calculus agents and delivered it under http://www.albertolluch.com/adr2graphs/

The underlaying techinque is described in a draft (http://www.albertolluch.com/papers/adr.caspis.pdf), where you find the credits to the original encoding by Fabio Gadducci and its rephrasing in our approach.

The visualiser is based on adr, graphviz and maude.