Dustproof/water resistant at depth equal to or greater than 1 meter.
Resistance to sweat makes it ideal for use while doing sports.
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
This measures barometric air pressure. It can predict weather changes, for example a sudden drop in air pressure could mean a storm is coming. When calibrated correctly it can be used to determine altitude, which helps GPS devices to lock on quicker and with greater accuracy.
An indicator shows you when the device has low battery.
The battery can be recharged and used over again.
A solar battery takes its energy from light, and stores it in a self-recharging battery which never needs to be changed.
With a stopwatch you can time yourself.
An altimeter can track elevation, ascent and descent using GPS or air pressure. It is particularly useful if you travel on hills or mountains.
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.
Waypoints are locations or landmarks worth recording and storing in your GPS. These are locations you may later want to return to, for example favorite restaurants, bars etc.
Garmin Fenix 5S Sapphire