There are quite a few apps and services selling personal carbon offsets, but most of them today rely on general surveys with questions such as "What kind of home do you live in?" or "How much do you drive per year?"
By combining data sources from Operating System for Climate Action, such as utility bills, driving records, travel data, and other sources of large carbon emissions, we could build an app which calculates a person or family's carbon emissions from actual data. This could then be linked to carbon offset purchases, either on a blockchain or separately, to offset emissions.