Olfaction is really amazing. (Even the crappy human version, to say nothing of e.g. canines.) We can build cameras that see better than eyes, microphones that hear better than ears, but there is no technology that comes close to matching a nose. Sure there are some special-purpose sensors that measure the precise concentrations of particular gases, but nothing so general as a what's found in all sorts of different animals. It's not even clear how to quantify smell, for that matter.