Well, Larni, I'm no IDer--I've never even played one in court--but my reference to aliens (Daddy?) above was not entirely tongue-in-cheek.
If we did have a methodology for detecting intelligent design, it could conceivably prove useful in extraterrestial exploration.
Alien life--and alien artifacts--may be, well, really alien.
To pick a sci-fi classic, what if we find crystalline forms that process energy from their environment for self-replication and other, mysteriously alien purposes--say, concentrating some trace element. Is this a mining operation? Is it life? Is it artifact? Is it both? Neither?
Assuming we do find extraterrestial life, we may have to consider the possibility that it was created or altered by an intelligence.
Having said that, I can't see how one would extract general principles of intelligent design (as applied to life-forms) without a data set of life-forms known to be designed by an intelligence other than our own.
As the fanciful crystalline scenario suggests, it would be useful to have an ID test when we are otherwise totally ignorant of the phenomenon and its natural context.
The simplest test seems to be the one we already have: Can we account for the phenomena with naturalistic causes? If so, we not only don't need to consider intelligent design, we have no valid reason to do so.
Guess I failed Advanced ID Theoretics after all.