I was on the lake, getting up to speed, watching the houses on the shore start passing by faster and faster, when I glanced down at the instrument panel; the speedometer said zero. An attempt at cleaning it out the following week had no effect. I resigned myself to the fact that I'd have to replace it. Of course, a fancy GPS would be far less likely to go bad and a lot more accurate. But then I discovered the inexpensive, handy-dandy iPhone app simply called speed.

The display is clear and legible, and it reads in both kilometers and miles per hour. You'll probably have to be moving at least 5 mph to get a reading, but you can rest assured that the GPS reading is definitely more accurate than the old-fashioned analog speedo you might have been using. The bonus is that you don't need a separate camera to "shoot" your speed reading; just hit the "menu button" and the "on/off" button on the top at the same time, and the iPhone's camera takes a screenshot. Couldn't be simpler.

– Mark Schweitzer