This is a very good app for any CFI, or pilot interested in analyzing their recent flights. I have flown all over the US now with CloudAhoy turned on, and later used the ample analysis tools to look back at vectors around traffic, deviations for weather, and landings, missed approach practice, and more. CloudAhoy is wonderful. You can look at a landing, for instance, from the point of view of an observer outside the airplane watching from almost any angle, or look at the cockpit view and "run" an animation showing an approach. I have used it with flight students to demonstrate stability in precision and non-precision instrument approaches, or flight in a traffic pattern.
I have used CloudAhoy on an iPhone (using the built-in GPS, and Bad-Elf GPS), and on an iPad 3 (using the built-in GPS, and also an external Dual GPS). CloudAhoy is really good at just working without a lot of fuss and setup. If you forget to stop CloudAhoy when you taxi off the runway, it will auto-stop on the ground after a short period of time. I have added pushing the "start" button on CloudAhoy to my checklist :-)
The developer (Chuck) not only answers email inquiries about CloudAhoy , but does so quickly and with enthusiasm. He has given us a really interesting and capable tool. This is a "must have" app for pilots.
DS (ATP - CFI-AIME)