The Black Eyed Peas star has been seen continually using the gadget on his wrist throughout the live shows, as well as his phone and iPad.
And on Saturday he took it to another level as pal Cheryl Cole phoned in to the show live on air.
While commercial channels are free to involve product placement on their shows, the BBC is banned from doing so over strict rules.
Will said of his watch gadget recently: “It takes my heartbeat, my calorie burn, you can make purchases from it. I started the company and funded it and used my own money to develop it.”
Speaking to The Sun newspaper, producers insisted they did not plan for Will to plug the device on air.
They said: “No one was more surprised than the producers when Will started talking on his watch phone. It’s not something we would agree with, but it just happened.
"Fortunately, no one has complained.”
You wait to the Daily Mail gets hold of it...
Meanwhile, Will also faced being rapped by bosses after swearing live on air... for the second year in a row.
“All of the coaches were warned before the live shows to be careful with their language, as there would be young children watching," a source said.