Use LEDs on Raspberry Pi as status for network based on ping/dns. The `/sys/class/leds/<led>/<file(s)>'` must exist!

As root.
```
crontab -e
```

Add the following lines.

```
*/5 * * * * ping -I wlan0 -c5 one.one.one.one && sh -c 'echo 0 | tee /sys/class/leds/ACT/brightness' || sh -c 'echo 1 | tee /sys/class/leds/ACT/brightness'
*/5 * * * * ping -I wwan0 -c5 one.one.one.one && sh -c 'echo 0 | tee /sys/class/leds/PWR/brightness' || sh -c 'echo 1 | tee /sys/class/leds/PWR/brightness'
```