http://gfycat.com/DelightfulLazyHarlequinbug
If you're too lazy to click a link, here is another gif.
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Pretty simple. The green blip in the center is you, the white blips are dudes moving around. If you don't move, or if you move carefully and slowly, you don't get pinged. I can adjust this if I have to. Marine armor has IFF(Identification Friend Foe) tags, so anyone wearing it doesn't get pinged. There are ~authentic~ pinging noises that can be turned off.
Currently it's just the little handheld device that you see near the bottom of the gif, the green/white circle. I am not much of a spriter, so that's just a placeholder. The tracker HAS to be held in your hand or it will shut itself off. Can't look at a motion detector in your pocket, now can you? This means that it can't be used with two-handed guns. I may see if I can make it able to be hooked up to guns like the flashlights.
I also considered making it battery chargeable, both to cut down on the potential performance drain and to make it less OP or whatever. I don't know if it would be, but who knows. Ideally there would probably be one tracker per squad. Maybe the engineer can lug it around.
The performance is okay. I had a little trouble with it, the main hog being the IFF, but I'm not sure how well it will profile on the actual server.
I'm tired and it is late so I will be leaving this here for the night.
I should probably mention that this is also just one dmi file, 111 lines, and a couple of icon files. It doesn't touch anything else, so it's just drag and drop, no hassle.