Land Rovers are the quintessential rough-and-tumble SUV that you could take to the trail as much as you could bring to the high street. Naturally, it should come with a key that you could bring along when you bike, kayak, heck, even swim. Meet the Activity Key.

The technology behind Activity Key is ingeniously simple: it’s a waterproof wearable that incorporates a RFID-based, battery-free technology used in times when the traditional key fob would prove to be inconvenient.

Vehicles equipped with Activity Key can be unlocked by simply holding the wristband to a hidden sensor in the bodywork. This then automatically reenables the previously de-energized key fob left locked inside, allowing the vehicle to be started.

A big surprise for Jaguar Land Rover is that up to 40 percent of owners are opting for this option—a four-fold rise from what the company expected. The Activity Key is available on the Land Rover Discovery, Velar, Range Rover Sport, Range Rover, and even Jaguar F-Pace and E-Pace.