The Complete Idiot's Guide to Geocaching notes the following helpful information.

"Expensive and elaborate gear is not required. More importantly, it should be easy to use, accessible, and durable. Outdoor gear gets seriously abused. Gear can get smashed in bags and packs, rained on, frozen, dropped in an icy river, and so forth."

Here's the wize scoop...
http://wize.com/gps-devices/?q=gps&up=gps