People do well breaking a habit (smoking, eating,etc) or getting a good one with support from a community.

Even just creating general forums for people to support each other around procrastionation will help see:

http://www.runnersworld.com/community/forums/runner-communities/marathoners/happened-tallahassee

You should probably look at the big picture of helping people meet your procrastionating goals and provide a more complete package of solutions than a browser plugin