We were able to test the "ECKey" system at the recent IFSEC show in Birmingham.

Once a phone has been paired with a control unit, which is done in the same way as pairing it with a head set, walking towards the receiver is enough to unlock it, while walking away locks it. Its security depends on the unique Bluetooth identifying number that mobile phones each have, but both the ECKey and the phone can be hidden from everyone else using 128-bit encryption or rolling codes.

The company was founded in 2004 by Dr Nick Willis, who holds a PhD in theoretical physics from the University of Cambridge, but who runs the company from New Zealand. Systems are available for use by up to 20 or 1,000 users and the range can be set from 1m to 10m. Locks can be made to unlock automatically or by entering a pre-selected PIN each time. If the phone is lost or stolen, it can be deleted from the lock.

Cost is £90 to £160 and the system was this year's "Access Control New Product" at the ISC West 2009 trade show at Las Vegas.