Apple has issued an ultimatum to Apple Watch developers. Starting June 1, 2016, all new apps for its smartwatch must be native apps built with the watchOS 2 SDK or later. New apps that don’t comply with the updated guideline will be rejected.
That may seem rather strict but it’s actually in the best interest of consumers.
Up until last September, all third-party apps were created using the original watchOS. As per that SDK, all of the processing for third-party apps was done on the companion iPhone.