With this in mind, there are several obvious key features for a beacon. The first and most important, is that it be small and light. This makes it convenient to embed in or put on the surface of a device, or to be worn by a person, most commonly on a wrist strap or as a lanyard. Consistent with that, the device needs to be low power. Batteries add cost, weight, and volume to a beacon, so minimizing power consumption, and thus battery size, will improve the ergonomics of product into which the beacon is being integrated. Long RF range is also important. It reduces the infrastructure cost, in terms of the number of gateways required to establish and maintain contact with the beacons, and facilitates applications in open spaces. Bluetooth^® compatibility is important as it makes it possible for the beacon to interact with the whole universe of existing Bluetooth devices like cell phones, laptops, and of course, Bluetooth gateways. Finally, it is desirable that the beacons be configurable over-the-air. Whether it is configured individually, like by a mobile device, or many at a time by a gateway, it is important for keeping devices up-to-date, including both feature and security updates.