The police use transmitters in patrol cars to send messages via Bluetooth between 30 and 100 metres away to any mobile phone or laptop with Bluetooth turned on and set to discoverable. In some areas, patrol cars are placed outside schools and colleges to specifically target youth, of which Bluetooth is a popular method of sharing photos, videos and multimedia content over the air.
While the technology is not new, nor is the method of transmitting messages, this use of technology shows that police across the world are recognising the use of wide-spread technology and taking advantage of the fact that many people use Bluetooth, though are not relying on it to inform citizens of vital messages.
Those with Bluetooth enabled and set to discoverable can see an incoming message from their police force via these transmitters and choose whether to accept the message or not. Though, some users choose to not enable Bluetooth as it can drain battery life and increase risk of contracting over the air viruses. It could also be argued that privacy could be invaded through these means, with suspicion of whether the police can detect your specific where-abouts.