You already have right to delete in this instance.
Here’s a quote from the NYT:
“You will always be in control of your data, and we will remain transparent about the data we collect and why,” Fitbit’s chief executive, James Park, said in an email to his company’s customers on Friday morning. “We never sell your personal information, and Fitbit health and wellness data will not be used for Google ads.”
A right to delete would mean something more like that the companies have no choice, e.g. that existing laws force them to delete your data from the service, whether they were willing to commit to offering that option or not.