The way it reads is that you will see people stealthed from range (at level 2 and 3)
I have level 2, and have been trying it for several days.
From my experience, all effects produced by this perk will only apply to people entering stealth near you.
I mean, not just the "sparks" from level 1, but the easier to see cloak effect.
If a guy enters your range already stealthed, nothing will happen.
So, I find this perk useless now