Portable electro-magnetic radiation sensor warning device

A light sensor warning device, comprising:

• a portable, compact, freestanding sensor housing configured to be stably and removably affixed relative to a metering device having a movable indicator element, the housing comprising:
• 1) a receiver for receiving light reflected from the movable indicator element, wherein the light comprises ambient or environmental light,
• 2) the receiver being positioned to define a reflective region within which the movable indicator element will reflect light toward the receiver,
• 3) a signal generator in communication with the receiver for generating a signal indicating that the movable indicator element is located within the reflective region,
• 4) a power source for powering at least one of the receiver and the signal generator,
• whereby the sensor warning device affixed relative to the metering device will generate a warning signal when the movable indicator element is located within the reflective region to indicate that the indicator has reached a predetermined level, and whereby the system does not require a light transmitter.