A built-in GPS (Global Positioning System), instead of an accelerometer that measures movement, will give more accurate real-time tracking information, with many GPS units informing you of the direction and distance back to your starting position.
A heart rate monitor will allow you to establish your own training zones to perform at your own best pace. A chest strap is more accurate than the wrist-based optical heart rate (OHR), but many athletes prefer the comfort and simplicity of OHR.
Best heart rate zones for running
Best heart rate training zones for cycling
Heart rate training: why early spikes happen
Using heart rate variability to optimise triathlon training
Many manufacturers have comprehensive post-session analysis software (e.g. Garmin Connect) via USB or wireless means (Bluetooth, Ant+ or even WiFi). You can also utilise a wealth of third-party apps such as Strava for live tracking and social media sharing.
Multisport watches offer button and/or touch screen usability to scroll through the watch’s main features. Check that the touchscreen doesn’t have a history of losing contact when scrolled with sweaty fingers or in the rain, and that data is displayed as clearly as possible.
Once you tip over the £100 price point, most models require USB charging via a charger bespoke to that manufacturer, usually clipping onto the side or back of the unit. Battery life can range from 5hrs to 20+ depending on how many features (i.e. GPS) you’re using.