That's because a team of researchers from Northwestern University in Chicago claim to have come up with a system that's capable of detecting when you're pretending to be active.
While the study was carried out with smartphones, it can apparently be applied to fitness trackers and smartwatches as well. The study involved participants trying to fake activity by doing things like shaking their phone in their hands or putting the phone in their pocket and moving their legs to set of the motion sensors.
Essential reading: How to cheat your fitness tracker
The research team were able to detect deceptive behaviour with a 84 percent accuracy in comparison to a 38 percent accuracy for detecting normal data.
According to Konrad Kording, a research scientist at RIC and associate professor in physical medicine and rehabilitation at Feinberg, this is a major breakthrough for the future of activity tracking, "This technology could have broad implications for companies that make activity trackers and insurance companies alike as they seek to more reliably record movement."
It's hoped that the system can aid insurance companies detect genuinely active customers to offer assistance. It would obviously be a good fit for doctors as well to keep an eye on patients who promised they'd get out of the house a bit more.
While the research could have a major impact on the evolution of fitness trackers, it's not entirely foolproof. That's according to lead study author Sohrab Saeb who said, "If someone attaches an activity tracker to a dog, the system can't recognise that."
So, no dogs allowed...