The free FltPlan Go app is an excellent resource for pilots who rely on the fltplan.com website for flight planning, since it automatically downloads and organizes navlogs from the website right on your iPhone and iPad. The app also offers a wealth of other resources, including flight tracking, FAA charts, checklists, airport/FBO directory and a weight and balance tool.
A recent update adds a new in-flight tool that allows you to visually estimate the tops of nearby clouds directly from your iPad. The new Cloud Tops feature is essentially a sight level that uses the accelerometers and built-in camera in your iPad to determine the MSL height of weather features around you.
The tool is very easy to use–hold the iPad so that the camera is pointing out the front window, line up the green level line with the top of the cloud, enter your aircraft altitude and estimated distance from the clouds, and you’ll then see the the height of the clouds displayed in large numbers at the top of the screen. Green means you’ll be flying above the clouds, red indicates you’ll be in the clouds, and orange is used when you’ll be right at the cloud tops. Cloud Tops automatically compensates for the curvature of the earth, so it’s just as useful too in the flight levels.
FltPlan Go is available here as a free download in the app store.