Just a tip, for anyone wondering how to get it working with wpTouch. The file to edit is wp-content/plugins/wptouch/themes/default/comments.php. This is where you stick your mcsp_html() call. Of course it will vary if you use a different theme, but hopefully this guides someone to the right place. (Like me, next time I do a re-install!)
http://wordpress.org/extend/plugins/math-comment-spam-protection/