gistfile1.tex

\documentclass{beamer}
\usepackage{lipsum}
\usepackage{tikz}
\usetikzlibrary{calc,shapes,positioning,backgrounds}

\usepackage[absolute,overlay]{textpos}
\setlength{\TPHorizModule}{1mm}
\setlength{\TPVertModule}{\TPHorizModule}
\textblockorigin{0mm}{6mm}

% show grid line.
\setbeamertemplate{background}[grid][step=10mm]

\newcommand\putblock[4][]{%
\begin{textblock}{0}(#2)%
\begin{tikzpicture}[overlay,remember picture,every node/.style={anchor=north west}]
\node (#4) at (0,0) [draw, #1] {#3};
\begin{pgfonlayer}{background}
\node at (0,0) [anchor=center,fill,circle,minimum size=3pt,inner sep=0pt]{};
\end{pgfonlayer}
\end{tikzpicture}%
\end{textblock}}

\begin{document} 

\begin{frame}[plain]

\tikzstyle{alert} = [fill=red!20, draw=red!60!black, thick]

\putblock       {10,10}{aaaaa bbbbb ccccc}{t1}
\putblock[alert]{70,10}{aaaaa bbbbb ccccc}{t2}

\putblock[ellipse]{40,30}{aaaaa bbbbb ccccc}{t3}

\putblock[ellipse callout, callout absolute pointer=(t3.south)]{40,50}{Notice!}{t4}
\end{frame}

\end{document}