HowMuch
Easy to use lite expense tracker with focus on daily weekly monthly yearly spending limit.
Codebase
The codebase of HowMuch is mostly written in kotlin and some parts are still in java. The app uses MVP architectural pattern similar to Android Architecture Blueprint for MVP. HowMuch uses rx-java and tries to be reactive as much as possible.
Design
HowMuch's design is highly "Material" and follows not all but many Google's Material Design Specs.