Its first wearable device will connect wirelessly to a user's iPhone and will be the interface for messaging, Apple says
Apple began taking orders at its Tokyo store in the morning, and was set to start global online reservations at 0701 GMT. First deliveries will begin in nine countries on April 24.
Dozens of customers had waited outside the Apple store in Omotesando for several hours before being ushered down into the basement one-by-one for what Apple called their trial fitting.
Users can also send a real-time display of their heartbeat to another Apple Watch.