You only need to find ONE person -- the person who will find the OTHER people you need.
But WHEN do you expect your product to come out., and why do you think people will buy it? By time you manage to get everything ready, Fitbit will have come out with a better version, and, perhaps, other companies will have, too.
You see, Fitbit already has a company structure in place, so they can move faster than you.
Meanwhile, a new burger place opened near my house recently. There used to be a fro-yo place at that location. Why didn't the fro-yo place succeed? Anyway, I learned of the new burger place when I got a coupon in the mail for a free soft drink with purchase of sandwich and side. Even with the coupon, it was $9 after tax. There was NOTHING special about the food. If I want a burger, I'll go to McD, BK, or Wendy's.
Why do people keep opening up burger places? I want a fast-food place that sells chicken cacciatore. You should consider doing that.