I think that the Motion Sensor Support Item is the easiest and quickest to complete, it's the one I just finished for the achievement. There are two feats, one for dispensing them, and the other for them detecting enemies. Dispensing is easy, after you throw one, wait for the box to fill then throw another. Throw one as soon as you spawn, then run somewhere else to throw another as soon as you can. I'd recommend playing Fumigation and tossing one at each of the points.
You need to dispense a total of 500, and have detected 2500 enemies with them, then this achievement will be yours!
If you're curious, you can tell which enemies you've detected by looking at your radar, normally enemies appear as small red dots, if they've been detected by your sensors they appear as larger red circles. If you really want to aim for this, any time you see some enemies detected by someone using the targeting goggles, go towards them and throw a sensor at them. Rather than get into a firefight right away, run to where your teammates are fighting, toss a sensor, then start shooting the baddies. It really just takes time to get this one, which makes it really pretty easy, and it's actually pretty useful in the objective gametypes, Fumigation and to a lesser extent Psych Warfare, less useful in TDM because the enemies can go wherever they please.