Ships don't survive by never being holed. They survive because the water stops at the next wall.
This checks your doors, not for burglars. No app can continuously scan a phone for intrusion from inside the phone — the operating system forbids it, and a tool that claims otherwise is running the same animation the scam pages run. What a phone can actually be checked for is posture: which doors are shut, which walls are up, and how far a breach gets before it stops. That is the thing you control, and it is the thing that decides how bad the day is.
Pick a device below, then work down. Nothing here is urgent — this is the work you do on a calm day so a bad day stays small.