Although smartphones can perform many tasks on their own, they’re also able to make devices such as drones, robots and cameras cheaper and/or more capable by acting as their “brains.” One of the latest gadgets to receive such a treatment is the humble – and potentially treasure-finding – metal detector. Presently the subject of a Kickstarter campaign, the Ukrainian/American-designed Air Metal Detector features a 9.5-inch (241-mm) submersible electromagnetic coil that is reportedly able to detect small metallic objects located up to 12 inches (305 mm) beneath the ground, or larger objects as far down as four feet (1.2 m). When such an item is detected, the Air Metal transmits a Bluetooth signal to the user’s Apple or Android smartphone, which is mounted on the handle. An app on that phone alerts users via an audible tone and an onscreen display, the latter indicating the type of metal and its depth within the soil. In order not to be bothered by alerts for things that they aren’t looking for, users can set the app to ignore certain metals or sizes of objects. Additionally, GPS coordinates of unearthed items can be recorded on the app for future refer...