The Halo band, which does not feature a display screen unlike most of its rivals, is priced at $99.99 (£75.70), while the app membership costs $3.99 per month, Amazon said.

The scope of growth in the fitness band market has prompted tech giants such as Apple Inc and Samsung to introduce many sophisticated features for health tracking, including electrocardiogram and blood pressure sensor.

In comparison, Amazon has featured a relatively new technology in the market called tone analysis, which reviews users' tone during conversations. When enabled, a microphone on the band listens to detect emotions such as happiness, confusion or affection in the speaker's tone.

It remains to be seen if consumers would embrace this feature or would it spark privacy concerns. Amazon said the technology was designed in a way that protects privacy.

The company said the water-resistant band, with a battery life of up to 7 days, also contains an accelerometer, a temperature sensor, a heart rate monitor and can measure body fat percentage.

Alphabet Inc-owned Google is also making strides into the fitness market. Google in November said it would buy Fitbit Inc for $2.1 billion, a deal that is currently under regulatory scrutiny.

The market is also crowded by cheaper offerings from China's Huawei Technologies Co Ltd and Xiaomi Corp.

(Reporting by Akanksha Rana and Munsif Vengattil in Bengaluru and Jeffrey Dastin in San Francisco; Editing by Krishna Chandra Eluri and Shinjini Ganguli)