WLPTDX - Miniature Pendant transmitter
datasheetprice each: $70  
Specifications
Dimensions 2.2" L x 1.42" W X 0.66" H (56x36x17mm)
Power one GP-23 12V alkaline battery (supplied)
Current Consumption 5 mA average while transmitting
Battery Life one year (typical)
measured range 250 feet minimum in open air
Accessories 30-inch neck chain
Operating Frequency 315Mhz