The SUAV is a gadget for the Recon kit. You unlock it after you get your first kill with a bomber on a China Rising map (thus gaining the Death From Above Trophy).
As soon as you have unlocked it you can equip it to your Recon loadout. It is basically a recon drone and as it has no weapons you need to get a Roadkill kill with it by running over, or running into, an enemy soldier.
I found the easiest way to do this was to look out for enemy snipers out on their own on hills.
You can only get this trophy by getting this kill on a China Rising map, it will not count if you get a kill with the gadget on any other map although you can equip it when you are on any map.
Update as per below:
"Worth noting, you must be Rank 10 before you can unlock the SUAV"