Dustproof/water resistant at depth equal to or greater than 1 meter.
Resistance to sweat makes it ideal for use while doing sports.
The device has an electronic display to present information to the user.
These devices will not experience water damage, e.g. in the shower. Devices which can withstand more water pressure are better for swimming or diving.
Polar RCX3 GPS
A compass is useful in games, map and navigation software.
The battery is removable and can be replaced by the user if broken.
With a world timer you can easily see the time all over the globe. It is useful if you are travelling through different time zones.