These days, almost every smart device has one or more sensors in addition to being connected to the Internet or to smartphones. Those sensors range from humble proximity sensors to more sophisticated, and more expensive, radars and "lidars". Mobile robots and self-driving contraptions are perhaps the biggest beneficiaries of such sensors, but those sensors do come cheaply. Well, they could, depending on how much you are willing to compromise. Researchers at MIT developed a laser distance sensor that, while crude, is quite decent for its price, which is only $49 plus a smartphone sacrificed to the cause.