A large black ball, originally designed by Swedish scientists for use on Mars, could be the latest weapon in the war against burglars.
The device, developed at the University of Uppsala, acts as a high-tech security guard capable of detecting an intruder thanks to either radar or infra-red sensors. Once alerted, it can summon help, sound an alarm or pursue the intruders, taking pictures.
It is capable of travelling at 20mph, somewhat faster than a human being. Even worse for intruders, the robot ball can still give chase over mud, snow and water.
The ball relies on an internal pendulum to control its motion which, when shifted, changes the centre of gravity and starts it rolling.
Other devices, including microphones, cameras, heat sensors and smoke detectors are mounted on its central axis.
Nils Hulth, co-founder of Rotundus, the company which is marketing the ball, said it was especially well-suited to patrolling perimeter fences.
The prototype, just under 2ft in diameter, weighs about 10lb. "It is extremely light, which is why it moves so fast," Mr Hulth said.
While the current version can only raise the alarm, it could be adapted to corner an intruder if the customer wanted, Mr Hulth added.
Patrick Mercer, the Tory MP who is campaigning to give people greater rights to defend their property against burglars, thought the robot ball could have potential: "It would be interesting to see whether the ball had used grossly disproportionate force or whether it would be deemed reasonable.
"But I would much rather a burglar be terrified of householders and shopkeepers, rather than some sort of futuristic device."