The best replacement for nike+ is fitbit.

The best alternatives to nike+ are rated as following:
★★★★★  fitbit
★★★★★  runkeeper
★★  strava
★★  runtastic
★★  micoach
★★  mapmyrun
★  endomondo
★  garmin forerunner
★  adidas micoach
★  forerunner 10
★  runmeter
  garmin 305
  fuelband

Your alternative for nike+ is not listed? Suggest!
Speaking about nike+, one probably shouldn't forget about nike shoes.

Other search terms related to nike+ and their ratings are:
★★★★★ nike shoes
★★ ipod nano
★ asics
You have in mind a companion for nike+ and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of nike+ in all years. Click on graph for more.
nike+
fitbit
runkeeper