What you're looking for doesn't really make sense. You need to take some time to think about what you're asking.
The behavior of the status LED is found on page 47 of the manual here: http://www.ni.com/pdf/manuals/373378d.pdf
During normal operation, the light is off.
2 flashes - software installation required
3 flashes - safe mode (code isn't running. this is a diagnostic setup state)
4 flashes - device is crashing
continuous flash/solid - unrecoverable error
In none of these states is code actually running on the device. You're asking for a way to read values from code that isn't running. It's like asking a car that isn't on to accelerate when you hit the gas pedal. It simply doesn't make sense.
You're looking for a way to see when the devices are running and when they're not. THAT is what you need. That is not equivalent to needing to see the status light. Stop focusing on something that won't help your solution and start looking towards something productive. If you continue to focus on this status light, you'll never be successful.
You'll have a better chance to achieve your goal by looking through the System Config VIs: http://zone.ni.com/reference/en-XX/help/373107E-01/nisyscfg/find/ I'd have to play around with them myself to figure out where the status of a device would be. It might be as easy as using "Find Systems" twice. Run it once with "detect online systems" false and it should omit the devices that are in safe mode. If you go through that returned array, you can parse the data to turn your LEDs off/on. It doesn't sound like you care which of the status flashes you're seeing as long as you know it's offline. That should be sufficient to turn the LED on or off.
