Handheld GPS Units

Handhelds are cheaper, smaller and lighter.  In  fact they may even be designed to help you keep track of your exercise or heart rate and may resemble a wrist watch or perhaps a PDA.

The compactness of handhelds are beneficial when carrying them in the outdoors but do not make them a good choice for driving.

Handhelds are great for campers, climbers, hikers, and bikers.  

Another type is the 'portable' GPS unit...