Bumping this as I purchased a fitness tracker in June. Wasn't sure which brand to go for but since my company was putting in Salesforce and some American fella at Dreamforce Light in London set Fitbit ran on SF I thought I'd try it.
Fitness trackers alone are not the answer, they do however provide motivated individuals with the ability to make educated decisions around diet and exercise. The gamification aspect also drives people on, so a bit of fun as well.
from biting a Fitbit HR to give me advanced notice of a heart attack, I am now 3 stone lighter, able to run 10k in 50 minutes and generally feel much better for it.