Math-o-mir is described as 'The Math-o-mir is a software tool designed to write and edit mathematical equations as easily as possible. The goal was to achieve the same level of simplicity as with pencil and a sheet of paper' and is an app in the Office & Productivity category. There are four alternatives to Math-o-mir for a variety of platforms, including Mac, Windows, Microsoft Office Word, Online / Web-based and Apple iWork. The best alternative is MathType. It's not free, so if you're looking for a free alternative, you could try LaTeXiT or Tex2Img.
MathType is a powerful interactive equation editor for Windows and Macintosh that lets you create mathematical notation for word processing, web pages, desktop publishing, presentations, elearning, and for TeX, LaTeX, and MathML documents.
LaTeXiT is a small utility that allows you to quickly typeset LaTeX equations, without bothering with file creation, preambles, and so on. The PDF image obtained can then be exported by dragn drop to any application supporting it.
Tex2Img is a free online Latex equation editor that converts Latex equations to high resolution images to embed in documents and presentations. You can also use Tex2Img to learn Latex by trial and error.