Yep, only for Platinum. There is no other code for it in any other game, I think. You can do it using PokeSAV in any game but that requires you to have a flash cart and I don't have that.
Basically, an AR code that reveals all data about a Pokemon in its summary (IVs, EVs, SID, etc.) It won't affect the mon at all so it's a safe code. There's really no legitimate way of checking SID aside from actual legit shinies so it's either that or AR.