Offsetting is a well known practice if you fly with a plane somewhere. But currently there is no one offering a offsetting service with an API. With an API and mini transactions there could be usecases like 'Offset your 231 Whatsapp messages from this month producing xxx kg CO²'
Work together with existing offsetting brands and just offer their service as an API
Cookieless user tracking example site
Show visitors of site how they can be tracked without cookies and that they can not do anything about that. Mainly as privacy awareness project
Learn new languages by learning the 1000 most used words in your favorite TV show
1) Get all subtitles from show in language you want to learn
2) cleanup data
3) most used word analysis
Thunderbird file provider plugin for 'Firefox Send'
It is emberrassing that the mozilla owned firefox send service can not be used as file provider in Thunderbird, but the users have to rely on a third party (e.g. Dropbox/WeTransfere) which have a lot worse privacy politics in place