Why not just buy a Polar, Fitbit or Garmin fitness tracking watch then? You don't really "sync" the Watch to your phone. The Watch is an extension of the phone. If you're not going to have your iPhone around you very often (and you say "old" - is it at least a 5?), it'd be real hard to justify getting it.
How old iPhone are we talking about though? Don't forget that it only pairs with the 5 or newer.
I have a 5.
The watch looks beautiful. All of the dedicated tracking watched look terrible. It can still work as a fitness tracker without the iPhone around right? I wonder how limited it will be on a disconnected state.