Have you tried making a FaceTime Audio call from your Watch? It doesn't let you right now as you need to do it from your iPhone. From how I understand it, with watchOS 2, you'll be able to start those calls from the Watch (regardless of whether you want to actually have them on your Watch with the small mic/speaker or your iPhone). I used FaceTime Audio a lot and when I first got the Watch I was disappointed to see that I couldn't say "Hey Siri, FaceTime Audio..." as I used to do on my iPhone.