A fork of Graph89 with UI and UX tweaks and fixes for modern Android versions. Graph89 is an emulator targeting the Android platform for TI89, TI89T, TI92, TI92+, V200, TI84+, TI84+SE, TI83, TI83+ ...
I use this a lot and love it a lot! The ROMs it emulates are very powerful calculators.
Also, there is a new project that brings Qalculate! to Android. You can find it somewhere here. It's also a powerful calculator and is more integrated to the system because it's not emulation.