A new sensor tracks and photographs every car that drives past your house. It appears to be legal but has raised privacy questions.

The BBC reports that the gadget from Flock costs $50 a year to use and the company says it will only make it available to “neighborhood leaders” with an emphasis on fighting crime. It says one person has already been convicted after being photographed driving away with a stolen bicycle in his open trunk.

At the moment the sensor will only take a photograph of passing vehicles and then log the time and number plate. Facial recognition could be added later.

Flock will reportedly allow local residents to opt-out of tracking but this won’t be available for cars that are merely passing through the area. Exactly how the law covers the technology may be open to dispute and could vary from area to area. In most cases in the US it’s legal to film or photograph anything that could be seen by a person standing in a public street.

The device is currently being trialed in Atlanta and the company is looking at getting investment before expanding availability.