Sporting events just wouldn't be the same without the tacky T-shirts, memorial cups, and foam fingers they generate. But do you ever actually buy any of that stuff? No. No, you don't. This year's U.S. Open might change that. The tennis tournament, which started on August 25, has inspired some of our favorite brands to create products that blend style and function. Below, a few pieces of gear (and one really great app) that might make tennis more fun to play than it is to watch.