Switzerland is an open source software tool for testing the integrity of data communications over networks, ISPs and firewalls. It can spot the I packets which gets modified by the ISP in case they are forging it out. This tool is released by Electronic Frontier Foundation. You can download this tool from here though you will need some skill to make it. Its some set of MAKE files which you would need to do yourself.
They also have a List of Public Switzerland Test Services where they have even added some bit torrent file which you can use to find whats with your ISP.
Its a good effort but I would have liked it more if they would have made it little easier for even normal users as of its only a command line tool.