I've worked to add altitude functions to Pebble Bike and it's is now time to share a first beta version to you.
(The link is included in the android app, but if you need it, here is the pebble app: http://labs.jayps.fr/pebblebike/pebblebike-1.2.0-beta1.pbw )
Things to be done:
Please note that an altitude provided by a gps is generally less accurate than one obtained from a barometric altimeter (an accuracy of 5 meters for example generally means a precision of 15 meters on the altitude).
Bad conditions (for example forests, cliffs or buildings) will degrade accuracy and then possibilities to calculate data based on altitude.
I've done lots of filtering on data to calculate a (cumulative) ascent that means something. As a result, during my last ride (1600m of ascent), the difference with a barometric altimeter was less than 2%.
Ascent rate (and slope) is more sensible to accuracy and could appear bugged.
Please try this first beta version and give me feedbacks!