How to control rosbag record from a topic?

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Hello ROS Community,

I am learning how to use ROS for controlling a UAV and have not been able to find any examples on how I might approach this properly. I'm not from a software engineering background so I have much to learn about programming still.

I would like to use a switch on my RC transmitter to start and stop recording a rosbag. I have the switch state being published under /mavros/rc/in. I have been able to access the channel and print out it's values with a node, however, I am having difficulty working out how to get the rosbag to initiate and stop correctly.

Is a node the best tool to use for this or would something like a service be more appropriate? Any suggestions on how best to start recording a rosbag when a topic is above a threshold and stop when it is below a threshold?

Any help would be greatly appreciated. Thanks in advance!

____________________________________UPDATE___________________________________________

I have got something working now. The updated code is below. Any suggestions for improvements however would be very welcome! Hopefully this can be useful to others in the future too.

#!/usr/bin/env python
import rospy
import rosbag
from mavros_msgs.msg import RCIn
import subprocess, shlex

class Monitor_Channel(object):
    def __init__(self):
        self.is_recording = False
        self.loop_rate = rospy.Rate(100)
        rospy.Subscriber("/mavros/rc/in", RCIn, self.callback)
        self.prev_switch_state = 0

    def callback(self, data):
        try:
            self.prev_switch_state = self.switch_state
            self.switch_state = data.channels[5] #5 is actually RC channel 6
        except:
            self.switch_state = self.prev_switch_state

    if self.switch_state > 1200 and self.is_recording == False:
        subprocess.Popen(shlex.split("rosbag record -O /media/nvidia/C61C-EBE4/recording.bag /mavros/imu/data_raw /camF/camera /camF/camera_info /camRR/camera /camRR/camera_info /camRL/camera /camRL/camera_info __name:=bag_record"))
            self.is_recording = True
            print("Recording data...")

    if self.switch_state < 1200 and self.is_recording == True:
        subprocess.Popen(shlex.split("rosnode kill /bag_record"))
        self.is_recording = False
        print("Recording stopped...")

    def start(self):
        while not rospy.is_shutdown():
            self.loop_rate.sleep()

if __name__ == '__main__':
    rospy.init_node("Monitor_Channel_6", anonymous=True)
    record_node = Monitor_Channel()
    record_node.start()