Psi-Emitter has moving parts in it... not very terget-ish. The Data Disc looks like a data disc to me...
ADDITION:
I got an idea...
What if I use the same effect as Tux did in his Rush, when you get transmissions from burrowed enemy units? That way, I'll get a click sprite in a blinking red circle. Any better?
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I think that would look cool. But then you might lag it if you have tons of targets and always have that thing running.