This is a basic app with a collection of common K-12 equations available at http://r-gaia-cs.github.io/math-cheat-sheet/. The equations are organized in sections and a table of contents is provided to help jumping from one section to another.
Although it is a basic app it is a nice way to show that Firefox OS supports MathML and create demand for some features not available right now like copy and paste (only the unstable version of Firefox OS supports copy and paste and the desktop version of Firefox requires the MathML Copy add-on), automatic line breaking and accessibility to users with disabilities.
The math authoring tool used in this app was TeXZilla, see section 1.4, because it allows the conversion of LaTeX into MathML and keeps the original LaTeX source code available. This is useful, for example, to copy an equation and paste it into Wikipedia.
Other nice features that can be added to this app in the future include:
link to resource like Wikipedia related to the equation,
search bar to quickly find the desired equation,
customization of equations, …