Grouptabs is an app to track expenses in a group of people.
When you share things with friends, just let one person pay and note the details in the app. Next time someone else pays. The app helps you keep the balance by indicating if you‘re currently on red or green. Ideally you never have to settle the tab. But of course you can.
Not everybody wants to share everything. Grouptabs lets you enter any constellation of participants for an expense. You can even add people on the fly. And have multiple people pay arbitrary parts of it. It's easy and flexible.
The app has been battle-tested in many scenarios over the last years but the current version is in an alpha stage. It is an offline-capable, installable web app and allows collaborating without user accounts. The user interface is optimized for phone-size touch devices.
The former version is very stable and in maintenance mode. For syncing with other devices it uses remoteStorage. You can collaborate on tabs by sharing a remoteStorage account.
Find the source code in the master branch.