I wrote a short example for the visualisation of a PostgreSQL 8.1.x GiST index
in GRASS.
It is not the most elegant coding but it works.
I'm open for new suggestions and ideas.
See:
http://www.sai.msu.su/~megera/oddmuse/index.cgi/GiST
http://www.sai.msu.su/~megera/oddmuse/index.cgi/PosGIS_and_Grass
Bernhard
p.s. special thanks to Oleg Bartunov