The deal for the device called "dial" was announced in Barcelona during the annual Mobile World Congress.
The gadget is will.i.am's second move into the smartwatch market after the celebrity launched "puls" more than a year ago.
Unlike most so-called wearables such as the Apple Watch, "dial" has its own SIM card so it can operate independently from another smartphone or tablet, for making phone calls or connecting to the internet.
The front man of the Black Eyed Peas launched "dial" through his technology start-up i.am+ and is tapping into a growing market for smart devices people can wear rather than carry.
Shipments of wearables are expected to grow from 84 million units in 2015 to 411 million in 2020, according to technology research firm CCS Insight. The global market will be worth $34 billion in 2020, up from $10 billion in 2015, they said.
Will.i.am's new device is voice controlled and can play music and surf the internet simultaneously. The operating system software can recognise and store personal preferences.
The smartwatch runs on a dedicated platform called AneedA, which includes a music streaming service, and also works as a voice assistant similar to Apple Inc's Siri and Microsoft's Cortana.
Will.i.am told a news conference he wanted to add more devices to the AneedA platform, but declined to elaborate.
The smartwatch was launched in Britain last week with operator Three.
Deutsche Telekom said "dial" would be available later this year in its European markets but declined to give more details.
© Thomson Reuters 2016