It's been suggested they were doing some sort of ESN sniffer attack to try to clone and steal a cell phone's ESN to make illegal calls. The area they were driving through is filled with apartment complexes with lots of college-age folk in them, so I imagine there were a lot of cell phones active at the time. After that it drifts into espionage sort of things or cyber attacks, but I don't even have an explanation for why or how those would work.