SplitBills is an Android app, which lets you split and organize your expenses with friends. Expenses can be organized into groups. A unique feature of SplitBills is that it works offline. Expenses can be synced over devices via XML files. Another advantage of this approach is that no central server is needed. The app can be found on GooglePlay and F-Droid. Below are some screenshots from the app:
The source code can be found on GitLab.