The bug report came in on a Tuesday. One line: "Your app says I hit 400 kmph. I was at a red light." He wasn't lying. Neither was the app. The phone genuinely believed it, and that is the interesting part. I work on mileage tracking. If you have ever had an app quietly log your drives for expenses or taxes, that is the category. Trip accuracy is not a feature of the product. It is the product. When we started, ours sat around 50 percent, and almost every missing point traced back to...