Four months after its newest Up bands started shipping — and nearly a year after they were first announced to the public — wearable tech maker Jawbone has rolled out promised features to its line of Up activity trackers.

The Up3 and Up4 bands, which are both equipped with heart rate sensors, will now track a wearer's heart rate periodically throughout the day, rather than just once in the morning as the wristbands did before. This "passive" heart rate tracking is supposed to give users a more complete picture of their health, including when diet or other stimuli might affect heart rate, the company says.

Also, the $180 bands will now automatically transition from active to sleep mode when the wearer goes to bed at night. Previously, users had to double-tap on the top of the device to set it to sleep mode, something that worked intermittently or not at all (in my own personal experience).

Finally, the Up3 will come in four new colors, including teal and sand; while the Up2 wristband, a $99 version without heart rate sensors, will ship with a thinner strap and will be available in six different colors. The clasp on the Up2, which was another criticized aspect of the product, has been redesigned, but until we get to try it out ourselves we can't say whether it's an improvement.

The changes are a delayed effort on the part of Jawbone to add more value to its newer Up wristbands, especially the Up3, which was introduced with high hopes but ultimately received tepid reviews after its launch in April. And while Jawbone's companion mobile app is often recognized as intuitive, comprehensive health-tracking software, Jawbone still struggles to compete with Fitbit when it comes to market share.

The feature upgrades, available through a firmware update, will roll out to users today through their iOS and Android apps, Jawbone says.