Incomplete untested version

import board
import digitalio
import dbus

# current button state
buttonPressed = False

# Init Button and LED
led = digitalio.DigitalInOut(board.C0)
led.direction = digitalio.Direction.OUTPUT

button = digitalio.DigitalInOut(board.C1)
button.direction = digitalio.Direction.INPUT

# Init systemd
# https://www.freedesktop.org/software/systemd/man/org.freedesktop.systemd1.html
# https://stackoverflow.com/questions/33646374/starting-a-systemd-service-via-python
sysbus = dbus.SystemBus()
systemd1 = sysbus.get_object('org.freedesktop.systemd1', '/org/freedesktop/systemd1')
manager = dbus.Interface(systemd1, 'org.freedesktop.systemd1.Manager')

def startService(serviceName):
    job = manager.StartUnit(serviceName, 'fail')
    print(checkState(serviceName))
    # Set LED state

def stopService(serviceName):
    job = manager.StopUnit(serviceName, 'fail')
    # Set LED state

# https://stackoverflow.com/questions/43499880/how-to-extract-service-state-via-systemd-dbus-api
def checkState(serviceName):
    interface = dbus.Interface(sysbus.get_object('org.freedesktop.systemd1', serviceName), 'org.freedesktop.systemd1.Unit')
    return interface.Get('org.freedesktop.systemd1.Unit', 'ActiveState')

while True:
    if button.value == True:     # if pressed the push_button
        if buttonPressed == False:
            startService("serviceName")
        else:
            stopService("serviceName")

Working with polling of current systemd status

mport dbus
import subprocess
import time
import board
import digitalio

from queue import Queue
from threading import Thread

RECORDER_SERVICE = "recorder.service"

# Init systemd
# https://www.freedesktop.org/software/systemd/man/org.freedesktop.systemd1.html
# https://stackoverflow.com/questions/33646374/starting-a-systemd-service-via-python
sysbus = dbus.SystemBus()
systemd1 = sysbus.get_object('org.freedesktop.systemd1', '/org/freedesktop/systemd1')
manager = dbus.Interface(systemd1, 'org.freedesktop.systemd1.Manager')

# Init LED
led = digitalio.DigitalInOut(board.C0)
led.direction = digitalio.Direction.OUTPUT

def startService(serviceName):
    manager.StartUnit(serviceName, 'fail')

def stopService(serviceName):
    manager.StopUnit(serviceName, 'fail')

def checkState(serviceName):
        while True:
                stat = subprocess.call(["systemctl", "is-active", "--quiet", serviceName])
                if stat == 0:
                        print("Recording")
                        led.value = True
                else:
                        print("Recording Stopped")
                        led.value = False
                time.sleep(2)

# Init Thread
t1 = Thread(target = checkState, args =(RECORDER_SERVICE, ))
t1.start()

# Testing
startService(RECORDER_SERVICE)
time.sleep(5)
stopService(RECORDER_SERVICE)

Added button case

mport dbus
import subprocess
import time
import board
import digitalio

from queue import Queue
from threading import Thread

RECORDER_SERVICE = "recorder.service"

# Init systemd
# https://www.freedesktop.org/software/systemd/man/org.freedesktop.systemd1.html
# https://stackoverflow.com/questions/33646374/starting-a-systemd-service-via-python
sysbus = dbus.SystemBus()
systemd1 = sysbus.get_object('org.freedesktop.systemd1', '/org/freedesktop/systemd1')
manager = dbus.Interface(systemd1, 'org.freedesktop.systemd1.Manager')

# Init LED and Button
led = digitalio.DigitalInOut(board.C0)
led.direction = digitalio.Direction.OUTPUT

button = digitalio.DigitalInOut(board.C1)
button.direction = digitalio.Direction.INPUT

def startService(serviceName):
    manager.StartUnit(serviceName, 'fail')

def stopService(serviceName):
    manager.StopUnit(serviceName, 'fail')

def checkState(out_q, serviceName):
        while True:
                stat = subprocess.call(["systemctl", "is-active", "--quiet", serviceName])
                out_q.put(stat)
                if stat == 0:
                        print("Recording")
                        led.value = True
                else:
                        print("Recording Stopped")
                        led.value = False
                time.sleep(2)

# Init Thread
q = Queue()
t1 = Thread(target = checkState, args =(q, RECORDER_SERVICE, ))
t1.start()

# Testing
#startService(RECORDER_SERVICE)
#time.sleep(5)
#stopService(RECORDER_SERVICE)

while True:
        if button.value == 5:
                if q.get() == 0:
                        #Stopping Service
                        stopService(RECORDER_SERVICE)
                else:
                        # Starting Service