Filed under: GPSEach week Ross Rubin contributes Switched On, a column about technology, multimedia, and digital entertainmentWhat do you get when you cross a portable navigation device and a cellphone? Dash Navigation's answer is the $399 Dash Express, the most credible attempt yet to crack the ancient driver conundrum of figuring out what's nearby and the best way to get to it. In doing so, it stands to elevate the portable navigation device from a glove compartment shut-in to a mobile mentor -- one that
