Here's a few things you should watch out for on iOS.
🟠 means your microphone is active
🟢 means your camera is active
If you see a blue pill-shaped indicator in the top right corner of the iPhone it means your device's audio, display, or location information are being sent off of your device to a remote server.
Also, you can check Settings -> General -> VPN & Device Management to see if there are any profiles installed on the device that you were unaware of.