i dont carry my phone around in my pocket all the time (sometimes i don't even have pockets to put it in) and im not sure how well a phone based step counter would work in my purse. especially when my purse is in a desk or on a counter somewhere where i am not.
my fitbit force, while basically a bracelet, is not something i would consider fashionable so i completely disagree with it being a fashion item. it's bulky and not something i wear to make a 'statement' at all. i wear it for functionality.
it tracks my steps and helps motivate me to move around and walk more. also, since i leave it on while i sleep, i can use it to track my sleeping habits (waking up a lot, etc). it also has a vibrate alarm that wakes me up without being loud or disruptive to anyone else.
i do agree about it being a little bit on the spendy side.
i do use apps on my phone for specifically taking walks, in addition to having the fitbit on, but thats because the phone does gps level mapping and i like to see where i went through the neighborhood and how that worked out in miles. the phone apps also provide a mph rate which i find useful for comparing when i walk with the dog vs walking with others vs walking by myself. if the fitbit could do those things, i would probably still use my phone for music.
as it is now, it works for me to use the two technologies in conjunction rather than feeling the need for one over the other.