Mathings is a simple no-frills editor for rendering snippets of LaTeX. Use the keyboard to type in the equations or text you want rendered. Then tap the Render button to generate an image.
Once you have rendered your snippet, you can either copy it to the clipboard or save it into your photo library. Now you can use that image in the document editor of your choice! This is a great way for adding equations to Apple's Pages or Keynote apps.