Surveillance

Surveillance equipment covers two very different jobs: recording what happens when you are not there, and observing a person or place as part of an investigation. The gear overlaps; the legal exposure does not.
What is in this category. Covert and overt cameras, body-worn and vehicle recorders, DVRs, long-runtime battery systems, audio recorders and the accessories that make them usable in the field.
How to choose. Start with the question you need answered, not the device. Proving who enters a stockroom after hours needs motion-triggered recording at a doorway with faces at usable resolution. Documenting a claim needs continuous recording with a reliable timestamp. Recording your own meeting needs audio, not video. Runtime and storage decide more outcomes than resolution: most failed placements ran out of battery or overwrote the event.
Where people get into trouble. Recording video where someone reasonably expects privacy — bathrooms, changing areas, bedrooms — is a crime everywhere. Audio is governed separately and more strictly. Arizona allows a party to a conversation to record it; other states require every party to consent, and recording a conversation you are not part of is generally unlawful. Placing a device on property or a vehicle you do not own or control raises separate issues. If the recording is meant for a case, ask your attorney before you start.
If it is going to be evidence. Set the clock, keep the original file untouched, work from a copy, and write down who placed the device, when and where. Self-collected footage usually fails on provenance rather than picture quality. For matters headed to court, insurance or an employment dispute, a licensed investigator collects it in a form that holds up: see private investigations and digital forensics.