In the very early hours of this morning I wrote a little LaTeX package that can add Gamst brackets to any theorem environment (well, I have tested this only with the amsthm package, but it should generally work with other packages providing theorem environments as well. The Gamst bracket is a large square bracket on the left side of a paragraph containing a theorem like statement. This type of highlighting was frequently used by one of my Professors when I was a student in Bremen, and this package is named after him.
Another feature of the package that is possibly more useful to most people is a macro that adds an end-of-theorem symbol to any theorem environment. This basically works the same as the little open box that marks the end of a proof in many journal style files or in the amsthm package.
The style-file and its documentation can be obtained upon request by email.