It's pretty cool. It's not used as much as it should be, but I blame people being new to it. You can salute, or if moving, you simply point. You can see your teamates on the map regardless of linked by SOP, but you only see them through walls with it. Once linked by SOP, you get updates on their status (knocked out, dead, unconcious, trapped by a magazine) and you give information from your SOP skills to them as well.
The SOP skills include Scanning, which is what you're talking about. It allows you to use a particular item while holding an enemy in CQC that hacks their SOP system and gives you and everyone you're linked to the locations of whoever that guy was linked to. It has limited duration depending on skill level. There are three other SOP skills, Aware (displays nearby traps, like claymores and magazines), Target Alert, and Enemy Exposure. I forget which of the last two is which, but one reveals the location of people you've attacked, the other reveals information on people who've locked on and attacked you.
Partially to brag, my animal rank is Bee. Which is obtained for using the S.S. Plug (the item for Scanning) numerous times. I've rarely ever had had enemy use a plug on me and I've never seen anyone else with the Bee animal rank. To even use it takes up one of your four skill slots, so most people don't bother. The benefits outweigh the risks at this point, but that may change as people get to know the game better.