the Fitbit mobile app
A stand-alone altimeter application that uses the built-in barometric sensor.
Displays current altitude and tracks minimum and maximum altitude. Due to natural pressure variations an initial error of several tens of meters can be expected. Use the right-side hardware buttons to adjust to a known altitude. Altitude changes can still be nicely tracked (since the natural pressure variation is slow). The red ball shows your relative altitude position within the min to max range that was recorded.
Includes a small graph of the rate of altitude changes in the last five minutes, and uses this information to show a weighted average that estimates your current ascent/descent rate in meters per hour.
Top left corner shows how many minutes the application is running, and top right the current time.
Enjoy the app, its free, but don't trust the readings for any serious activity.
Fell free to send me photos of your treks and altitude readings to email@example.com or Twitter @xmal