2) I primarily built it for myself, and I mostly do weight training at a gym. So there are a few features that may be helpful for interval training (superset support automatically advances forwards and backwards when you add a new set, rest timer buzzes when its time to get going again), but I'm not sure how helpful v1 would be for you. I want build on this to make it useful to as many people as possible. I'm not very familiar with Simple Fit, so if you have any ideas on how a voice controlled logger would ideally meet your needs, please let me know.
3) Sure. The idea came about pretty simply -- I tried out every possible workout app because I don't like carrying a pen and paper around with me. I found every one to have the same weakness -- they require you to take out your phone/ipod after every set to input data. I was already using a headset with a microphone to listen to my music while I exercised, so I figured why not put it to use? I didn't validate the idea at all. I figured that worst case scenario, I would build an app that allowed me to track my own workouts and manage my progress how I wanted it to be done. I did the development myself over the course of several long months. One of the features that I find most useful is that saying "skip track" will automatically skip to the next track in itunes. Because the iphone/ipod dont have hardware skip buttons, this is really helpful because I used to have to take out my ipod, unlock it, go to the music app, and tap skip. There are a few features like this and I don't think I would have been able to come up with them unless I was building it for myself and constantly testing it and finding its weaknesses.