Fitbit's Charge HR and Surge just became smarter thanks to the firm's latest software update, Digital Spy reports.

Once the new software is installed, the wearables will have enough brains to automatically detect which activity the user is engaged in.

The so-called SmartTrack system helps Fitbit's flagship trackers distinguish between running, outdoor biking, walking, aerobic exercise and sports - no more fumbling around through menus to manually select your workout.

New smarts isn't the only update to the Charge HR and the Surge. Both devices also benefit from improved heart-rate monitoring thanks to the introduction of PurePulse optical technology.

Fitbit has also revamped its app for iOS and Windows devices to include weekly exercise goals. This feature is coming to Android in the near future.

The fitness tech firm has certainly been busy, as new blue, tangerine and teal versions of the Charge HR accompany the software updates, along with blue and tangerine Surges.