Aura Reading sounds too much like Power rather than a Stunt (like a specific use of
The Sight or a visual type of
Supernatural Sense). If your wanting a Stunt that allows using Alertness for Empathy checks, I'd call it
Noticing the Little Things. Alertness is passive, where making an Empathy check for someone's aspects I'm fairly certain is active. So the checks would be made by you or you tell them to make it.
Investigation might be more appropriate substitute for Empathy Reading because, as I said before, Empathy Reading is more of an active use of a skill where Alertness for perception is passive. I'd call it
The Devil is in the Details or something similar.
Personally I'm just more comfortable using Lore to see if I have supernatural knowledge of the person/creature I'm attempting to read or just use Empathy outright.
And reading
Unity of the Senses, it is just substituting Alertness instead of Lore for the passive
presence or absence of the Supernatural, which a normal person can do with Lore anyway.
((Slightly off topic but seeing that the Temple Dog's Alertness is less than Harry's Lore + Arcane Senses Harry should have sensed the One Ear before puppy Mouse in
Blood Rites, unless Mouse's Alertness is higher than the average Temple Dog
))