This app simulates an aircraft altimeter!
It displays your current altitude via the devices GPS.
Beyond that, it also displays the various types of altitudes used in aviation such as:
It also include settings to vary parameters which determine these important altitudes thus allowing students and pilots to really see the difference between them and the effects of temperature and pressure on altitude.
We've all heard the old adage:
"From hgh to low or hot to cold, look out below!"
Now see it brought to life on your IPhone.
What a great training aid for instructors!
Have a great flight!