Check out more Sensors Converge coverage.
STMicroelectronics' TMOS sensors handle presence sensing using a 5- to 20-µm passive IR sensor. This provides more accurate results as well as information about the distance rather than just a basic threshold typically provided by other technologies.
In this video, ST's Tom Bocchino shows off the STHS34PF80 (Fig. 1), including discussion of this low-power TMOS sensor's operation.
The module can detect object up to 4 m away without a lens, and up to 6 m for assumable human body sizes. The SMD-mountable device is capable of distinguishing between stationary and moving objects. It has an 80-degree field of view and is calibrated in the factory.