The reason you don't do all simultaneously is they all will likely suck, and then you have to redo three apps instead of one.
I would think you would want to do one mobile app just right, and then port it to other platforms. You might do a spec for all three up front so you think through each platform, but why not push one platform, iterate, and then take what you've learned before building?
I would think you would want to do one mobile app just right, and then port it to other platforms. You might do a spec for all three up front so you think through each platform, but why not push one platform, iterate, and then take what you've learned before building?