Originally delegated work for One Penny Per Mile's Green Driving app c. 2011. Requires GPS. Matching sources for this app are in my github account.
GT2, a full app was brought to level v 2.0.0 as described at github in August 2021 and development is active and ongoing from that point. Unlike the original GT2 works on both android and iOS.
As noted at github, this will not work on Android 10 or versions of that OS where you can't get to the app settings menu (3 dots), required to start a trip.
This original app is slightly better at tracking position than the first version of the new one but doesn't even calculate the CO2 value.
Has historical value only.