While in run mode, just put a little box in the corner that will allow you to tell zwift how fast your treadmill is moving. That would eliminate the need for foot pods and Bluetooth phone apps and make it super convenient for zwifting away from the home on a gym or hotel treadmill just using your iPhone.
There is an app for iPhone called Treadmil Smart Speed. This will do the job, but keep in mind you’ll need a seperate iOS device, you can’t run it on the same one as Zwift.
I’ve been using that app to run on zwift since the zwift iOS version was released. My point is it would be great to bring one device into a gym and run on zwift. Have the same functionality of the treadmill speed app built directly into zwift. Just two little arrows that allow you to adjust the speed of your runner to the speed of your treadmill.