Modern Altimeter GPS+ app is for folks who care for hiking and biking in mountainous terrain.  GPS is getting very accurate in terms of  distance indication.

Link to companion app https://itunes.apple.com/us/app/altimeter-pro-pebble-edition/id993492455

We would like to introduce you a simple and precise speedometer, working as well on smartwatch pebble!

Correct and easy to use altimeter