I have a IOS application with a companion WatchOS application. I am wondering if there is a way I can communicate with the IOS application while it not running as a foreground application.

My situation right now is that my IOS application is connected to a bluetooth device. This device can only be connected to one thing at a time. I want the IOS application to handle all bluetooth communication. I also would like to have the WatchOS send data to the IOS application while, the phone is locked or the application is in the background, to tell it to send data to the bluetooth device.

Is there any way to do this?

I don't think so, but your watch can access data via the network. Perhaps you might be able to find a way to use that to keep the watch app updated?

https://developer.apple.com/documentation/watchkit/keeping_your_watchos_content_up_to_date