Yeah, there are several out there that would manage that. To be honest, so does my Droid Incredible phone. Not great topo maps, but it can find its way around—and do audible turn-by-turn navigation in the city.
A really good dual-purpose unit is the Garmin Oregon 450t. It's designed primarily as a high-end backcountry GPS, with preloaded topo maps and the ability to store up to 1,000 waypoints and 200 routes. Color screen, GPS accuracy to ten feet, waterproof construction. For auto use, snap in a Garmin MapSource SD card and you have all you need for turn-by-turn in-town navigation.
The Oregon is a bit steep at $500, but it's an awfully nice unit. The Garmin Dakota 20 offers some of the same mapping and backcountry/auto capabilities in a lesser unit for $350.
Another unit that can handle multiple tasks is the Magellan xPlorist 510 ($350). It has excellent GPS reception, a three-inch touch screen, and comes with complete U.S. roads. And you can add maps from Magellan's backcountry Summit Series, or road-intensive City Series. Each is $100.
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