Server-side "greasemonkey"-type service

Hi all -

Just as Opera do pre-processing of pages before they go to Opera Mini, 
or Greasemonkey alters the HTML of pages in Mozilla - are there any 
server-side services that could allow us to semantically markup sites 
that we know could be augmented with RDFa for scuttering?

For example, let's say we wanted to put MySpace pages through a parser 
that would inject FOAF RDFa as per some template?

Any ideas?

John.

-- 
Dr. John Breslin
DERI, NUI Galway
http://sw.deri.org/~jbreslin/
john.breslin@deri.org