Persistent i3blocks blocket displaying VPN connection status

i3blocks-vpn.sh

#!/bin/sh

ON='{"full_text": "", "color": "#00ff00"}'
OFF='{"full_text": "", "color": "#ff0000"}'

dbus-send --system \
    --print-reply \
    --dest=org.freedesktop.NetworkManager \
    /org/freedesktop/NetworkManager \
    org.freedesktop.DBus.Properties.Get \
    string:org.freedesktop.NetworkManager string:PrimaryConnectionType \
| sed -n '1d;s/.*string "vpn"/'"${ON}"'/p;t;s/.*/'"${OFF}"'/p'

dbus-monitor --system "\
    type='signal', \
    sender='org.freedesktop.NetworkManager', \
    interface='org.freedesktop.DBus.Properties', \
    member='PropertiesChanged', \
    arg0='org.freedesktop.NetworkManager'" \
    2> /dev/null \
| stdbuf -oL sed -n '/"PrimaryConnectionType"/{n;s/.*string "vpn"/'"${ON}"'/p;t;s/.*/'"${OFF}"'/p}'

i3blocks config

...
[vpn]
command=/path/to/i3blocks-vpn.sh
interval=persist
format=json
...