The best replacement for fitbit flex is force.

The best alternatives to fitbit flex are rated as following:
★★★★★  force
★★★★★  jawbone up
★★★★  nike fuel
★★★  one
★★★  jawbone up24
★★  fitbit one
★★  zip
★★  force review
★★  polar loop
★★  fuelband
★  garmin vivofit
★  up24
★  up
★  nike fuelband
★  jawbone
★  nike fuel band
★  fitbit force
★  bodybugg
★  polar
★  bodymedia
  polar watch
  polar ft4
  vivofit
  withings pulse
  fitbit force review
  fuel band
  fuelband se
  misfit shine
  jawbone up 2
  nike fuelband se
  up by jawbone

Your alternative for fitbit flex is not listed? Suggest!
Speaking about fitbit flex, one probably shouldn't forget about myfitnesspal.

Other search terms related to fitbit flex and their ratings are:
★★★★★ myfitnesspal
★★★ biking
★ my fitness pal
You have in mind a companion for fitbit flex and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of fitbit flex in all years. Click on graph for more.
fitbit flex
force
jawbone up