In 2014, the Treasure Tag accessory for Windows Phone owners was released by Nokia, just before their Devices and Services division was acquired by Microsoft. It used Bluetooth to allow owners find their smartphone if they misplaced it. Now Microsoft is apparently developing a more advanced version of the accessory, as a device labeled as the "Treasure Tag Plus" recently was filed with the Federal Communications Commission. There's no word yet on when Microsoft will announce or launch the new device.
Aside from the name, the only other major thing about the FCC filing was that Treasure Tag Plus will have a circular shape, compared to the square device that Nokia made for the original Treasure Tag. We can assume that the new version will continue to use Bluetooth to assist in finding a smartphone. Microsoft has updated the official Treasure Tag app since the launch of the accessory and added a way to use the button on the device, while the Lumia Selfie app is running, to take a picture with their smartphones.