The barometer and altimeter

The barometer and altimeter have a chart mode as well where you can see a time history of readings. Very useful for hiking profiles, keeping an eye on the weather trends, and no doubt impressing your friends.As noted above, the GPS performs best when the watch has a good view of the sky. That combined with the battery life leads me to recommend this for activities like biking, sailing (and boating in general), general aviation and use as a backup navigation instrument.Other watch features (stopwatch, dual-time, alarms, time zones) all work great and are as expected.Although I like the Suunto X9i, there are some drawbacks and annoyances. First off, the 100m water resist rating only applies if the buttons are not pressed. In other words, you can't actually use the watch in the water at all. This is a glaring annoyance in an otherwise well-engineered watch, and we hope Suunto fixes the issue in the next model. Secondly, the inte***ce is sluggish, and combined with hard-to-press buttons, makes for a sometimes-frustrating user experience. It's hard to navigate when you can't tell if the button was pressed or not. Thirdly, the GPS receiver sensitivity is considerably worse than even older handheld units, and fails to work in places where a handheld has no problem.On the other hand, it works great with clearly sky visible, has a very readable and usable display, and can do amazing tricks like "display a backlit digital compass in the dark" that are super useful for outdoors types and geeks alike.