Home Depot offers the Belkin WeMo Home Automation Switch for iPhone, iPad, or iPod touch 2-Pack, model no. F5Z0432-BF-HD, for $59.98. Coupon code "HDHOLIDAY" cuts the price to $54.98. With free shipping, that's $42 under the lowest total price we could find for this quantity elsewhere, although we saw a 2-pack for a buck less in September. It operates over WiFi and mobile Internet to turn electronics on or off from anywhere.
Update: It's now available for in-store pickup only.