[JavaScriptFunctions] any WG implementations / advocacy?

I was just taking a look at 
http://www.w3.org/2009/sparql/wiki/Feature:JavaScriptFunctions which was 
submitted on our -comments list by Holger Knublauch of TopQuadrant.

The gist, as I understand it, is asking implementations to dereference 
URIs of unknown FILTER functions to retrieve RDF descriptions that 
contain JavaScript implementations of the functions.

I think this is pretty cool, myself, but it also seems very new, a very 
high burden for implementors, and potentially fraught with security 
concerns that I haven't thought of yet.

I'd like to know if there are any other implementations of this feature 
(which, to generalize a bit, I'd call a mechanism for interoperably 
resolving unknown SPARQL functions) and also if there are any Working 
Group members who care to advocate in favor of the group producing a 
specification for this feature.

Lee