Reporter Jane Slater found out just how well the fitness tracker works after noticing her ex-boyfriend's activity levels spiking at 4 a.m.

NFL Correspondent Caught Ex Cheating on Her Because of Activity on His Fitbit

Fitbits do a great job of tracking steps, sleeping patterns, heart rate, and more — sometimes documenting activities so well that the device can show when somebody has been unfaithful.

Earlier this week, NFL Network reporter Jane Slater recounted a story on Twitter about how she found out that her ex-boyfriend had cheated on her thanks to the popular fitness tracker, which revealed what he was really up to at 4 a.m.

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The sportscaster, 38, shared her story after responding to another NFL reporter’s Tweet about how his wife had enjoyed being gifted a Peloton bike — a nod to the controversial holiday ad — countering that she did not have a good experience when it came to fitness-related gifts.

“An Ex Boyfriend once got me a Fitbit for Christmas. I loved it,” she wrote, adding that while she “loved it” at first, things took a sudden change for the worse one day.

“We synched [sic] up, motivated each other… didn’t hate it until he was unaccounted for at 4am and his physical activity levels were spiking on the app,” she said, adding she “wish[ed] the story wasn’t real.”

“Spoiler alert: he was not enrolled in an OrangeTheory class at 4am,” she quipped in a follow-up message, referencing a popular fitness class which could have explained her ex-boyfriend’s activity levels.

While Slater admitted in a later Tweet that she “sobbed uncontrollably” at the time, she now laughs when she looks back on the story.

“It’s a story my friends and I def laugh about now,” she shared with one user.