What does Groovy have to do with Informix?
For one, we can develop applications in Groovy accessing IDS since it can use the JDBC driver (or the common data server JCC driver).
Second, the Groovy community has put together an eclipse plug-in that allows you to edit, compile, and run groovy scripts and classes. According to their web site (http://groovy.codehaus.org/Eclipse+Plugin), it works with Eclipse 3.3 and 3.4 but not with 3.2.
For what I can tell, the latest version of IBM Data Studio Developer (version 2.1) is based on Eclipse 3.4.1 so it should work fine.
Third, we should be able to use Groovy to write user-defined routines. I admit, I did not try it but if you compile the Groovy code and make the Jar file that implements Groovy available either as part of the UDR or in the onconfig classpath, it should work fine.
If you want to start playing with Groovy, take a look at the following site:
Let me know how it goes...