Works well. Make sure you use a well lit area. You need something to hold the iPhone like a tripod. Usefull tool for anylizing your fit on a bike as long as you know what to look for. Use sticky dots on yourself will make it much easier and accurate. The app has good instructions and is well worth the asking price of 2.99. Even if you only set up saddle height its worth it. btw should be between 155 to 145 degrees or 25 to 35 degrees from straight leg.