I have found Gevel, a tool enabling the visualization of the content of the GiST indices in Postgres. In particular, I am interested to use it to visualize the RTree spatial index in PostGIS. Does it work with Postgres 2.0? Is there a simple way (not compiling from source) to get it to run (e.g., with postgis.app on Mac OSX?) Apparently, Gevel and the rtree-gist modules should now be part of the default Postgres distro as per the readme, but I cannot find any way to enable these.
EDIT: Following on from comments, if I have to build from source, do I have to build while building Postgis, or can I add gevel later.