I was at Staples today picking up a replacement mouse and they had the new Garmin nuvi 500’s out. These rugged little units do it all, they come preloaded with topo AND road maps for the lower 48 and you can upload maps for other areas. They are waterproof rated at IPX7 which is “Immersion for 30 minutes at a depth of 1 meter”, so it can certainly handle rain or a wet backpack. And since it comes with the topo maps preloaded you will almost certainly get it wet hiking or walking your favorite city.
You can get the windshield mount for your car, then just pop it out when you want to go for a hike and throw it in your pocket. The screen is 2.8” x 2.1” and the unit is less than an inch thick. It has a user replaceable, rechargeable battery with a mini USB port for charging. It has all of the standard road features like calculate route, “avoid this road”, shortest time, shortest distance, find address, find food, find gas, etc.
For $254 you really can’t beat the price. I don’t need a new GPS, BUT if I did, this unit would be at the top of the list.