Researchers have produced a mobile phone that could be a boon for prying bosses wanting to keep tabs on the movements of their staff.
Japanese phone giant KDDI Corporation has developed technology that tracks even the tiniest movement of the user and beams the information back to HQ.
It works by analysing the movement of accelerometers, found in many handsets.
Activities such as walking, climbing stairs or even cleaning can be identified, the researchers say.
The company plans to sell the service to clients such as managers, foremen and employment agencies.
"Technically, I think this is an incredibly important innovation," says Philip Sugai, director of the mobile consumer lab at the International University of Japan.
"For example, when applied to the issue of telemedicine, or other situations in which remotely monitoring or accessing an individual's personal movements is vital to that service.
"But there will surely be negative consequences when applied to employee tracking or salesforce optimisation."
Until now, mobile phone motion sensors were capable of detecting only repetitive movements such as walking or running.
The KDDI system, is able to detect more complex behaviour by using analytical software - held on a server back at base - to match patterns of common movements.
For example, the KDDI mobile phone strapped to a cleaning worker's waist can tell the difference between actions performed such as scrubbing, sweeping, walking an even emptying a rubbish bin.
The aim of the new system, according to KDDI, is to enable employees to work more efficiently and managers to easily evaluate their employees' performance while away from the office.
"It's part of our research into a total ubiquitous technology society, and activity recognition is an important part of that," said Hiroyuki Yokoyama, head of web data research at KKDI's research labs in Tokyo.
"Because this technology will make central monitoring possible with workers at several different locations, businesses especially are very interested in using such technology to improve the efficiency of their workers.
"We are now at a stage where we can offer managers a chance to analyse more closely the behaviour of staff."
KDDI says it is in talks with a Japanese employment agency that specialises in contract cleaners and security and is interested in deploying the new technology.
"Of course there are privacy issues and any employers should really enter into an agreement with employees before using such a system," Mr Yokoyama told BBC News.
"But this is not about curtailing employees' rights to privacy. We'd rather like to think our creation more of a caring, mothering system rather than a Big Brother approach to watching over citizens."
It is not the first time remote spying technology has been enlisted by employers to keep an eye on their workforce in Japan or elsewhere.
Lorry drivers are regularly monitored through mobile phones in Japan, while salespeople have been regularly tracked by their employers using GPS since it was introduced to Japanese mobiles in 2002.
Critics of such systems accuse the makers of pandering to an over-controlling, Big Brother-type managerial class and say that with this new technology there comes the increased opportunity for abuse.
"This is treating people like machines, like so many cattle to be monitored and watched over," Kazuo Hizumi, a leading human rights lawyer, told BBC News.
"New technology should be used to improve our lives not to spy on us.
"It beggars belief that a prominent company such as KDDI could come up with such a surveillance system. It's totally irresponsible."
Japan had a very poor record on human rights, privacy issues and consumer rights, said Mr Hizumi.
For this reason, he said, invasive technologies were readily accepted as there was little debate on their possible impact to be found in the media in Japan or among its people.
"I'm afraid ordinary citizens don't care about this lack of rights. Consequently because of technology like this, Japan is heading for the Dark Ages," said Mr Hizumi.