PricePlunge offers the Utilitech Dusk-to-Dawn Security Light with Outlet Receiver 2-Pack, model no. 45164, for $11.99. Coupon code "homerun5" drops it to $11.39. With free shipping, that's $1 under our mention from a month ago and the best price we've seen. (It's a current low by $6.) 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 $7.99 with free shipping. Code "homerun5" drops it to $7.59.