There are lots of product that you can get for surveillance to name some of them
Digital Surveillance Camera
Spyglasses
Telephone voice changer
Telephone Recorders
Child Safety
Child Guard™ Monitor
KinderGard Home Safety Kit
Knives
Folding Knives
Pen knives
Butterfly knives

These can be very usefull for bank or big companys or very for home use .
Can you add to this list