Whistle-reactive key fob, in case your keys are lost, all you need to do is whistle loudly. As soon as the device recognizes your "search signal", it will immediately emit a sound accompanied by flashes of the built-in LED light, which will help you easily find your lost keys. The device works at a distance of up to 7 meters. If you go farther away, it is unlikely to wait for a response. The kit already includes 2 batteries and a ring for attachment.