Here's one possible solution that will draw the squiggly line and admits page breaks (well, one at most) in the affected paragraph(s); all you have to do is to enclose the desired paragraph(s) inside \Startsquiggly, \Endsquiggly:
\documentclass{article}
\usepackage{refcount}
\usepackage{tikz}
\usetikzlibrary{decorations.pathmorphing,calc}
\usepackage{lipsum}
\newcounter{tmp}
\newcommand\tikzmark[1]{%
\tikz[overlay,remember picture] \node (#1) {};}
\newcommand\Startsquiggly{%
\stepcounter{tmp}%
\tikzmark{a}\label{a\thetmp}%
\ifnum\getpagerefnumber{a\thetmp}=\getpagerefnumber{b\thetmp} \else
\begin{tikzpicture}[overlay, remember picture]
\draw [decoration={coil,aspect=0},decorate,ultra thick,gray]
let \p1 = (a.north), \p2 = (b), \p3 = (current page.center) in
( $ (\x3,\y1) + (.55\textwidth,0) $ ) -- ( $ (\x3,\y3) + (0.55\textwidth,-0.5\textheight) $ );
\end{tikzpicture}%
\fi%
}
\newcommand\Endsquiggly{%
\tikzmark{b}\label{b\thetmp}
\ifnum\getpagerefnumber{a\thetmp}=\getpagerefnumber{b\thetmp}
\begin{tikzpicture}[overlay, remember picture]
\draw [decoration={coil,aspect=0},decorate,ultra thick,gray]
let \p1 = (a.north), \p2 = (b), \p3 = (current page.center) in
( $ (\x3,\y1) + (.55\textwidth,0) $ ) -- ( $ (\x3,\y2) + (.55\textwidth,0) $ );
\end{tikzpicture}%
\else
\begin{tikzpicture}[overlay, remember picture]
\draw [decoration={coil,aspect=0},decorate,ultra thick,gray]
let \p1 = (a.north), \p2 = (b), \p3 = (current page.center) in
( $ (\x3,\y3) + (.55\textwidth,.5\textheight) $ ) -- ( $ (\x3,\y2) + (.55\textwidth,0) $ );
\end{tikzpicture}%
\fi
}
\newcommand\Squ[1]{\Startsquiggly#1\Endsquiggly}
\begin{document}
\begin{itemize}
\item \lipsum*[1]
\item \Startsquiggly\lipsum*[1]\Endsquiggly
\item \lipsum*[1]
\item \Startsquiggly\lipsum*[1]\Endsquiggly
\end{itemize}
\end{document}

The code might need two or three runs for the lines to stabilize.
\beginsquiggly(....)\endsquigglyor\squiggly{....}comes to my mind... These would also be al lot easier to remove later on. So this, if I might say so, is not a duplicate. – Christian Apr 19 '12 at 13:26leftbarenvironment from theframedpackage. See Alignment in theleftbarenvironment. Isrightbarpossible? for an example. – Werner Apr 19 '12 at 14:12[highlight]and some more text to title for improved retrievability. considered adding tag[changes]or[change-bar]but didn't since those have the opposite intent although the appearance is basically equivalent. – barbara beeton Apr 19 '12 at 18:07