Hello All, Let me preface this post by saying I have already done a considerable amount of research on this topic and have yet to get a logical answer to my question. In hopes that someone will be able to assist, I have tried to make this post as concise as possible by breaking my thoughts into the following sections: background, calibration methods, and where I see a flaw in the Apple/Nike logic. I look forward to any and all constructive input! Background: I purchased a 32GB iPhone 3GS on the day it was released this past June. On August 1st I bought the Nike+ sensor and a pouch for my New Balance running shoes and went for a run the next day. At the time I really wasn't thinking about it in detail, but selected calibration, chose a 3 miles distance, and went for a run. At the end of my run when the phone registered 3 miles, I ended the workout and my phone showed it was calibrated. Over the past several months I have wracked up about 350 miles. From time to time I though it was a bit odd that runs along the same route over the same amount of time showed slightly different recorded distances and pace, but I assumed it was a slight lack of precision on the part of Nike and Apple. This past Saturday, I set out for a 8 mile run, and was disappointed when I found that almost 1.6 miles into my run, the app had only recorded 1 mile. By the end of my 8.55 mile run which I confirmed with GMAP pedometer and later with my car's odometer, my iPhone Nike+ app had only recorded a 6.45 mile run, and informed me that my pace was around 12:35/mile (much slower than my avg running pace of 8:30-9:00 min miles depending on distance and how much I drank the night before. This was clearly the worst of all previous inaccuracies - off by 2 miles! At first I thought my sensor battery was going, but Nike/Apple say you get 1000 hours of use, and I had only wracked up a cumulative 55 hours. Then I thought my phone needed a re-boot, but as I was near the Apple store I popped in for a chat with a Genius. Now I know better than to think I am going to find any runners at the Apple store, but after a logical discussion with the guy we agreed it could only be 3 things - the sensor, the phone's Nike+ receiver, or the app. So, he replaced the sensor for me. The next day I went out for another run, and mid run my iPhone (for the first time ever) completely locked up. Not one of those hard-resettable lockups, I mean DEAD, never to come back to life. I went back to the Apple store, and 10 minutes later was given a new iPhone by another genius. Now I am sure we can all agree, we have addressed software corruption, iphone hardware and the sensor. The next day I ran again. Everything started off great, the "one mile complete" prompt came up at the point that I know to be 1 mile (give or take a few strides), but by mile 3, 4 and 5+ I could tell the accuracy had really slipped. At the end of my 6.45 mile run, the phone only showed 5.6 miles ... better than the other day, but still not accurate. During this few days I've described above I had been communicating my problem with a Nike+ tech support rep. He told me that the inaccuracy was because I did not have the chip in my shoe and that a pouch was unreliable. Not a bad way to sell Nike shoes, but his logic about recording every strike through the shoe's design made a little sense. I was willing to accept this somewhat, but admittedly it seemed odd after 350 miles of pretty accurate runs. Anyway, not thinking, I set out to calibrate my iPhone again. On the iPhone you can select Calibrate, then Run, and then choose the recommended 400 meters or set a custom distance greater than 400m. I selected 400m and took off. As I ran, I waited and listened for a prompt from the phone: "300 meters to go, 200, calibraraton complete, etc." It never came! When I finally looked at my phone I had gone 3/4 of a mile. This is when I started to really think about what was happening and it hit me ... WHAT THE HELL IS THE POINT?? Documented Calibration Methods: According to the Nike+/iPhone 3GS FAQs on both the Apple and Nike site, to calibrate the phone you select Calibration and then choose Run or Walk. If you choose Run, you are then asked to choose the distance to calibrate. The choices are 400 Meters or Custom Distance, which allows you select a distance to run. You then begin your run and end it, APPARENTLY, when the phone tells you that you have reached the distance. As I stated above it does not tell you, you need to look at the screen and determine if you've gone that far, and then you end the workout ... and viola, you're iPhone is calibrated. On the iPod Nano, selecting calibration is done in similar way. The difference with the Nano is that you are required to determine on your own a location that will allow you to run a certain distance and then run it. When you have completed the distance (pre-determined to be X) you look at what your Nano has recorded (Y) which might be more or less than X and you dial the Y distance up or down to equal X. This process correct the Nano's readings and calibrates it. The Flaw in Nike/Apple Logic with regard to the iPhone 3GS: From the research I have done online and talking to techs, at no point does the Nike+ app use the GPS built in to the 3GS. The iPhone/Nike+ system measure distance by foot strikes, which determine pace. The phone uses pace and time to determine distance. This is why the Nike+/3GS works on a treadmill even though you are not going anywhere. Fine! But when it comes to calibration, the logic of it all goes to hell. In order to calibrate the PACE, you need the element of time and distance. Time is of course being measured, but without GPS or the ability to correctly dial in a distance, how is the pace calibrated? When I ran today 3/4 of a mile, the only thing that was measuring how far I ran was my foot strikes (pace). You CANNOT calibrate pace with pace. Therefore, there is no way to calibrate the system. Stated another way, if I measure 400 meters, using some undefined method that we agree to be accurate, and then I run it using my 3GS and Nike+ and at the end look at my phone to see that the app has only logged 350 meters, there is no way to tell the phone it is wrong. If I end the workout, it says that the phone had not calibrated because the distance was not sufficient. If I were to do it again and continue to run another 50 meters until the phone registers 400, it will "calibrate" the phone, but it is still inaccurate because I really ran 450 meters. I'd like to know if anyone else has thought about this and if there is an answer that makes sense. I secretly hoped that calibration pulled from the phone's GPS, but I have been told time and time again that is not what happens by Apple and Nike techs. Further, if that was the case, why the hell wouldn't the 3GS tell you when your calibration was complete as opposed to letting you run right through the calibration distance? It just doesn't add up. I find this whole thing very disturbing. I also find it a little nauseating that the Nano Nike+ software is more powerful and accurate than the app for my iPhone. Can someone please explain the logic here? I'm I missing something, or should I just buy in to the whole "the software knows what it is doing" argument - which is complete BS! Thanks in advance for any assistance any of you can provide.