Attention all tech startups heading to SXSW: Walter wants to meet you. Walter is a pop-up agency that will run for five days. It’s the brainchild of JWT and consists of employees from the agency’s New York, Atlanta, London and Brazil offices. In the short window, Walter will meet with 25 tech startups, and narrow them down to a few finalists. The winners will have a marketing and media strategy built for them.