Quick Answer
What can modern security cameras do that older ones cannot?
Modern cameras record in high definition, see usefully in near-darkness, and stream to a phone from anywhere, so a property can be checked in real time rather than reviewed days later. They flag motion in defined zones instead of recording hours of empty footage, which makes finding an incident fast. Recordings are kept digitally as a searchable history for insurance and police. Higher resolution also means footage is detailed enough to identify people, not just movement.