Fitbit has announced an update to last year's Alta fitness-tracking wearable that adds heart rate sensors into the mix. The Alta HR will be available in April, starting at $150, and essentially brings the functionality of the Fitbit Charge 2 into a more compact (25% smaller) design --- the optical sensor lays almost flush on the underside of the band, unlike the prominent bump under the larger Charge 2.

The new band comes in 10 styles including four different colors in the floppy, entry-level elastomer bands, three colors available in leather for $60 extra and three stainless-steel models priced at $250. All models have a tap-sensitive, OLED display and seven-day battery life.

In terms of features, aside from the new heart rate monitoring capabilities, the Alta HR can also show smartphone notifications, track steps and introduces a new function called Sleep Stages. The latter works in conjunction with the optical heart rate monitor to offer more detailed sleep tracking data --- Fitbit will take motion data, along with heart rate variability, to show light, deep, and REM sleep stages.

Sleep Stages is also coming to the Blaze smartwatch and Charge 2 later this month. Another new feature called Sleep Insights is supposed to draw a direct line between your daily activities and your sleep patterns, but that's not tied to your heart rate so every Fitbit user will get it with an upcoming app update.