1). Make a map.
2). Right click the map and select its properties.
3). Select the sun bar which should be white.
4). Now in the color box choose a color thats darker than white. I prefer dark grey.
5.) Press ok and go to the area on the map in which you want the alarm.
6). Set a light in the desired location.
7). On the light properties uncheck currently turned on.
8). And click the light color and choose what ever you want. I recommend red given its an intrusive color.
9). Click present and select pulse.
10). Now were it shows the time erase the "10 seconds" and put 2.
11). Okay now for the actual sensor. Put a zone were you want the alarm to trigger. This will be the trip switch.
12). double click "touched by playable charactor" and click insert event.
13). find the "turn on/off light" trigger and double click it.
14). Select the alarm light or what ever you named the light. and check the circle "turned on"
15). Wala theirs your alarm system. you may also make it disabled by adding the "disable zone" in one of your script. If you need further assistance a video is shown below:
http://www.youtube.com/watch?v=151fB02OkDA