Background Vario uses your phones Barometric sensor to measure altitude with very fine accuracy. It then reports altitude and vertical speed within defined intervals using text-to-voice. For instance, you can set the app to report every gain or loss of 200ft and it will read out "one thousand eight hundred feet", "two thousand feed", etc etc as you climb.
This app essentially serves as a replacement for your standard "beeping" variety variometer. The virtue of this way of doing things is you can listen to music, talk on radio, or otherwise use audio devices without constantly having to deal with beeping in the background.'
When you first start the app, it will calibrate using GPS. GPS will sense your altitude within +/-100ft (with a good signal), and the barometer will take over after that.This initial calibration can take up to a minute depending on how good your GPS reception is. Periodically while you are using the app the altitude will be re-calibrated with the GPS. You can set the interval on which this occurs in the settings.
Background Vario will only work properly with Android devices equipped with a barometer. Please see a listing of Android devices with a barometer here: