A new ambient sensing technology called Sensify could make this easier by turning your light bulbs into motion sensors. And it might be landing on a Philips Hue bridge near you very soon.

TP-Link also offers fancier ones that can change hues as you see fit. Have more than one light bulb socket that needs to be filled? This affordable pair of bulbs from Fitop should serve you nicely.

But if you could shrink one down to the size of a light bulb, you could easily dot them around the porch using the existing sockets and wiring ... R2 and R4 on diagram), so the dimming function ...