altatac via eBay offers the Oregon Scientific Elements Wireless Indoor / Outdoor Thermometer
, model no. EW91, for $13.49
with free shipping
. That's the lowest total price we could find by $2, although it was a buck less in January (since expired). This thermometer includes an LCD indoor and outdoor temperature display screen, icy conditions warning, and more. It supports up to three outdoor sensors (one sensor is included).