A drone surveillance system can spot violence in a crowd, including stabbing and strangling, but some worry the consequences have not been thought through

Infrared cameras are the heat-sensing eyes that help drones find their targets even in the dead of night or through heavy fog. Hiding from such detectors could become much easier, thanks to a new cloaking material that renders objects -- and people -- practically invisible.

Walmart discounts a selection of Star Wars toys, apparel, movies, video games, and more as part of its Force Friday Sale. Choose in-store pickup to dodge the $5.99 shipping fee, or bag free shipping on orders of $35 or more. A couple of best bets:

• Jakks Big-Figs Colossal Star Wars 48.5" Darth Vader Figure for $59.97 (low by $10)
• Air Hogs Star Wars RC Millennium Falcon Drone for $67.11 $65.27 (pictured, low by $8)

Note: Participating Walmart retail locations will host a Force Friday weekend event, with games, activities, and giveaways. Click here for formation.

DJI Official Store via Newegg offers the refurbished DJI Mavic Pro Quadcopter Drone with 4K Camera for $799 with free shipping. That's $196 under the lowest price we could find for it new. It features a 12.7-megapixel camera with 4K video recording, top speed of 40mph, run time of up to 27 minutes, and control range of up to 4.3 miles.
Note: No warranty information is provided.

GearBest offers the MJX B3 Bugs 3 RC Quadcopter in Black bundled with a Deluxe Action Figure for $82.99 with free shipping. (The figure will add to your cart automatically.) That's the lowest price we could find by $28 for the drone alone. It features two-way 2.4GHz RF, a 20-minute flight time, and a camera bracket. The doll can be used for drawing practice. Deal ends September 21.
Note: This item ships from China and may take two to three weeks to arrive.

Walmart offers the Star Wars Air Hogs Star Destroyer Drone for $22.97. Opt for in-store pickup to avoid the $5.99 shipping charge. That's the lowest price we could find by $15. It features a 2.4GHz remote, light-up LED thrusters, and 250-foot range.

RCMoment offers the MJX Bugs 2C 1080p 2.4GHz 4-Channel Brushless Quadcopter Drone for $199.99. Coupon code "MJXBS2C" cuts it to $114.99. With free shipping, that's the lowest price we could find by $18. It features a 1080p camera, 6-axis gyro, brushless motor, GPS-assisted postioning, return-to-home function, and up to an 18 minute run time. It includes an 8GB TF card.
Note: This item ships from China and may take up to four weeks to arrive. The countdown timer on the product page does not reflect an actual expiration time and resets daily.

Walmart discounts a selection of Star Wars toys, apparel, movies, video games, and more as part of its Force Friday Sale. Choose in-store pickup to dodge the $5.99 shipping fee, or bag free shipping on orders of $35 or more. A couple of best bets:

• Jakks Big-Figs Colossal Star Wars 48.5" Darth Vader Figure for $59.97 (low by $10)
• Air Hogs Star Wars RC Millennium Falcon Drone for $67.11 $65.27 (pictured, low by $8)

Note: Participating Walmart retail locations will host a Force Friday weekend event, with games, activities, and giveaways. Click here for formation.

DJI Official Store via Newegg offers the refurbished DJI Mavic Pro Quadcopter Drone with 4K Camera for $799 with free shipping. That's $196 under the lowest price we could find for it new. It features a 12.7-megapixel camera with 4K video recording, top speed of 40mph, run time of up to 27 minutes, and control range of up to 4.3 miles.
Note: No warranty information is provided.