I have just purchased an 'ardcase that completely encases the pedals. It looks pretty well made and the material is off a decent guage that would prevent only the most motivate of thieves from stealing your pride and joy. Ultimately it doesn't matter what you do, if they want it that badly they will have it. These things only prevent the opportunist thieves.
http://www.mudstuff.co.uk/'ardcase.shtml
http://www.mudstuff.co.uk/'ardcase.shtml