Linger via Amazon offers the Vensmile Ultrasonic Pest Repeller for $35.90. Coupon code "UQKVIHL7" cuts it to $22.98. With free shipping, that's the best deal we could find by $20, although we saw it for a buck less in February. This device purportedly repels mice, roaches, and other pests via a high-impact pressure wave and ultrasonic sounds. It covers unobstructed areas measuring 5,000 to 6,000 sq. ft. Deal ends April 16.