I have an iOS application which is dowloading data from server using SOAP technology. This data I need send to apple watch every minute but iOS application have to be at background. Use of background fetch is not posible solution because iOS decide the time where background fetch is executed. I know that timer at background will be stoped in 3 minutes. So why I ask here. My boss dont trust me that sending data every minute with timer at bachground is impossible. Thanks for answers.
It's not impossible but any app that does that will not be allowed on the app store. Apps are only supposed to run in the background for a limited time (3 minutes, as you say.)
If you set up your app as a background audio app and play a "silent sound" then you can run in the background indefinitely, but that is a misuse of the entitlement.
Keeping your iPhone app running in the background would drain the battery quickly. Likewise sending a message to the watch every minute would chew through the watch's battery faster than normal. BLE is burst mode and pretty power-efficient, but the watch likely has to go into high power mode to handle the communications.