Lighting Occupancy Sensors
Occupancy sensors are typically smaller and less powerful than full-fledged motion sensors. Generally, they are used indoors to provide light on demand in hallways, stairwells, bathrooms, janitors closets and other places where it may not be convenient or practical to flip a switch. These sensors can also do their part in enhancing security by alerting you when someone has entered an area.
A typical occupancy sensor looks like a 4 or 5 inch half dome and sticks a mere two inches out from the wall. They often have two or three 1/2 inch threaded sockets for small lights right at the source. This type gets you 180 degrees of motion sensitivity so it can "look" up and down a hallway 40 feet long and 25 feet across. A vandal proof lens will help keep the device from malicious attacks. It helps to have a sensor that can work with dimmers and electronic ballasts.
A more compact version looks like a simple wall switch plate without the switch. The sensor is good for up to 20 feet which makes it ideal for small spaces such as bathrooms, closets, and stairwells. It would also be effective in a short passageway.
For a wider range, get a ceiling mounted sensor with a full 360 degrees of view. Set in the center of a room, it can detect entrances from multiple points and monitor motion over the tops of cubicle walls. These sensors can scan a 25 or even 50 foot radius, responding to motion from anywhere within. This makes such sensors ideal for hallways as well. A single such motion sensor could cover an entire 100 foot hallway.
You can even get a simple kit to retrofit your below cabinet lights to work with a motion sensor. Suddenly, a dark workshop with a switch at the far end is no longer a series of hazards to be navigated. Walk across the floor in safety and flip the lights on.
All these occupancy sensors should come with an adjustable time delay. You may want the lights to stay on just long enough for someone to reach a switch if they want to (say, 10 seconds). Or you may want a single motion to keep the lights going for 15 minutes, giving you ample time to work. (If you get lost in thought for longer than that, just wave your arms and the lights will come back on.)
As with outdoor motion sensors, make sure that whatever motion sensor you purchase is rated to control the number of watts you plan to attach to it.