The DIY and the Pro alarm systems both do have a port available for a LED light to show if the alarm is armed or not. By adding a relay you can also switch a bigger light on when armed and off when disarmed.
Please take note that this is be a wired connection and wires will have to be installed from the LED to the panel. The status LED also should have current limiting resistor (560 Ohm) else the LED will blow.
It is worth keeping in mind that the pro system uses the PGM port that can be used for switching something when the alarm is triggered or when the alarm is switched on/off. The pro do have the capability to have up to 8 switched connected with it.
Very view people use LED status lights, in older days the status LED played an important roll as you can see that your alarm was triggered and you thus have to be cautious when entering the premises, today you receive a sms to inform you that your alarm was triggered.
A status LED on a pro or DIY system can show you armed or disarmed status but not a trigger status. The functionality of a trigger event is now taken care of as explained earlier by receiving a sms and/or phone call from the alarm system.