A small comment on wording: I think this should be called "Electrical nose stimulation". In a medical context, "digital" tends to refer to fingers. I found out the hard way that a digital anal exam involves no electronics.
> Or, as the researchers suggest, a mapping application—smell your way home.
This would be the perfect sensory augmentation for Andrew Quitmeyer's "Mark Your Territory" project: Pee to Check-In to Foursquare, using the Checkin Gradient to navigate, so you could smell your way to nearby locations where your friends most recently peed.
I don't follow. What's stunning about it? Doesn't it just mean that there is little evolutionary pressure or selection on the olfactory receptor genes? Not sure what the discovery is, or its significance.