Suggestion: An inexpensive, weather protected cell or land line phone type dialer (possibly created from old/used cell phones) could be wired into the motion detector circuit. A pre-designated number is dialed when the light turns on. The cell phone would be constantly charged by the a/c current available at the floodlight power source. The land line would not require charging.

I know that it is common for security equipment to dial phones when alarms go off. However, this concept would be based upon inexpensive home motion detecting electronics, used/disposed of cell phones, or telephone land lines. I would hesitate to have the cell phones dial 9-11 (though non-subscribing cell phones supposedly have that ability in the U.S.) due to chances of the 9-11 lines being flooded with false alarms.

Similar low cost setups for automobiles could be created using obsolete cell phones and inexpensive motion detectors.