PricePlunge offers the Utilitech Dusk-to-Dawn Security Light with Outlet Receiver 2-Pack, model no. 45164, for $10.99. Coupon code "SANDCENT1" cuts that to $10.44. With free shipping, that's a buck under our April mention and the best price we've seen. (It's a current low by $5.) Each receiver features a sensor that turns your lights on at dusk and automatically turns them off at a set time. They also feature a 100-foot range and require one A23S battery each (included).
Note: You can add a single light receiver to your cart for $7.59 via the above coupon, with free shipping.