Pant Saver Invention Foiled!

I have been going on a lot of interviews in the city and that's great but what to do with my poor pants and feet. My dress pants and most of my pants in general are very long. I like my pants long but if I want to wear sneakers, which I do, I'm in trouble. The other morning I had the idea of pinning the back hem of my pants up with.... Bobby Pins! It worked pretty well actually. Except that the pins slipped a bit over time. So, here I thought, I'll invent a better version only to find that there seems to be one already: Zakkerz http://www.zakkerz.com/. Damn!  I think I'll have to give them a try.  Anyone ever use them?