The majority of bosses would happily examine their employees' health app data if they thought they were faking sick leave.
A survey of 619 UK business leaders found that 55% would use the chance to snoop on the technology if they could catch staff pulling a sickie.
Of the UK businesses quizzed by Astellas Pharma, 72% said they gave all or some of their employees a mobile phone.
Two thirds (63%) added that they invested in keeping their employees fit and healthy by offering: running clubs and cycle to work schemes (34%), gym memberships (21%) and healthy challenges (7%); smart watches, health apps and allowances; or by buying things to keep them fit and healthy (7%).
However, when UK bosses were asked how likely they would be to look at the health data from an employee's smart watch or health app - such as measuring how many steps they took, their heart rate and body temperature - if they called in sick, over half said they would be very or fairly likely to check the data in order to confirm that the employee was telling the truth.
Unsurprisingly, just 6% of employees would want their boss to have access to any health data generated from a mobile phone or smart watch.
Ken Jones EMEA president and chief executive officer at Astellas Pharmasaid the firm took the health and wellbeing of its employees very seriously.
"Like many of the businesses that we surveyed, we also invest significantly in our workforce to ensure they lead happy and healthy lives.
"In my experience, to have a successful business you need to have confidence and trust in your employees, confidence that they can do their job and trust that they are likely to turn up for work. We're all in no doubt that new smart health technologies and the insights they provide hold the key to improving the health of people, but at what point does smart data become intrusive surveillance? This is why a debate is needed," he added.