If other people are able to produce with a graph of real time data with Wi-Fi, while yours is only capable of recording one data point, then it may not make the product indispensible enough for people to use, or pay for it. You are basically competing against all fitness companies out there who already have a large ecosystem of partnerships.
let's take this one question: Nike is a standard app that comes with the iPod/iPhone. what is it about your app that makes people want to use it, as a complete replacement or as an additional value to this app?
i think to approach this one problem, I would probably draw the focus of my app into an "analysis" piece, and steer away from solely being a "data recording" piece. By being an analysis piece of software, you could look into fitness devices out there, pull data from different types of fitness devices: from exercise equipments, to fitness accessories. this could potentially be a huge win if you could pull it off. it doesn't mean that you can't provide image recognition as an additional feature, it just means that's not where the core value of the app is.
Second question, there are already these fitness social networking communities who are already doing some of this already, how do you plan to compete with them? For example, from their front page, dailymile says that it works with garmin, nike...haven't read about what this means, but my guess is that they already have these devices plugged into their social community. what kind of values can you provide here? if your app allows people to record and analyze data no matter what social community they belong to, then it might be pretty valuable.
of course i haven't done much research so i am just pulling things out of my head without giving these things a whole lot of thought. if you start thinking about making a product that is "indispensible" then it will attract a lot of fans