The company's rationale is simple: systems based on smartcard technology can easily be cheated, but those that match a name to a face are harder to foil.

'Even with smartcard technology, there's nothing to stop someone from giving their card to a co-worker to check in for them,' said chief executive Thomas Wan Wah-tong. 'But with a camera, the employers will know that it's the same person with two cards.'

Potential buyers include construction sites with many temporary workers to manage and mainland factories that employ up to 100,000 workers.

But shirkers take heart: Hectrix has yet to include facial-recognition software with its system, meaning employers would have to manually check photographs against a database to ensure their workers were not cheating the time clock.

Given the daunting nature of that task, the time clock is more of a deterrent than a fool-proof way to catch dishonest workers.

Employees who gripe about loss of privacy are likely to be told to find a job elsewhere, but the technology becomes a concern when used as a part of secure access systems, such as in apartment lobbies or at schools.

Guidelines published by Hong Kong's Office of the Privacy Commissioner for Personal Data allow for the monitoring of domestic helpers, but employee monitoring undertaken without reasonable cause 'raises privacy concerns and, if not handled carefully, may damage relationship between employers and employees'.

A commission spokeswoman said using biometric information, such as finger scans, was 'privacy intrusive' and should not be used simply for recording attendance.

'Obviously it depends on the context. It might be necessary for controlling access to a mint or a gold vault, for example, but if it's used just for cleaners at a school then I think it's unnecessary,' the spokeswoman said.

'The point is that there are generally less intrusive alternatives to achieve the same results.'

Hectrix would not reveal sales figures for its camera-equipped time clocks but claimed demand was strong.

In addition to integrating the clocks as a part of access control systems, they can also be tied to payroll and human resources databases.

'The whole interface is web-based and works exactly like a browser,' Mr Wan said.

'Basically, the package is plug-and-play and you can buy one of our terminals off the retail shelves and start using it.'

He envisioned a market for the devices in homes once costs come down, for 'people who employ part-time domestic helpers and don't want to stay at home just to make sure that the helpers show up on time'.

Schools that have explored the use of radio frequency identification tags as a part of attendance systems could become big adopters of the technology.

Hectrix is in discussions with several schools in Detroit, Michigan, and hopes to land an order for 1,000 units.

'If a student hasn't checked in by 9am, for example, the system can automatically send an SMS to their parents,' Mr Wan said, adding that several schools in Hong Kong had also expressed interest.

He believed privacy concerns would eventually be overcome. 'Sooner or later it won't be a problem,' he said.

'If you were to say 20 years ago that England will have surveillance cameras in the streets, no one would have believed you. But now England's inner cities are the most monitored in the world, and I believe the rest of the world will follow that trend.'