How to show a placeholder instead of an equation?

Question

I am looking for functionality similar to the endfloat package but for equations. Instead of displaying an equation I would like to display a placeholder such as

[equation 1 here]

Does anyone know of such a package?

Answer 1

The following works for the standard equation environment, but not for other math environments:

\documentclass[a4paper]{article}
\let\oldequation\equation
\let\oldendequation\endequation
\renewenvironment{equation}
  {\setbox0=\vbox\bgroup\oldequation}
  {\oldendequation\egroup\[\hbox{[Equation \theequation\ here]}\]}
\begin{document}
\begin{equation}
x=y
\end{equation}
\end{document}

I can't think of any application.

Answer 2

Not sure if this is what you meant, but you want to add reminder in the document to go back and actually add the equation there, then the todonotes package would be useful.

\documentclass{article}
\usepackage{todonotes}

\begin{document}
\todo[inline]{equation 1 here}
\end{document}