Jailbroken phone to jailbrake iwatch makes sense and is the only route that I see possible.
I would like to have the ability to link more than one iphone to my watch. I usually carry two phones with me so it deosn't makes sense buying two watches.
It would also be nice to be able to pick and choose what sensors on the watch are on or off. Even put the sensors on a scheduale. It is also to give us the right to protect and choose what data we choose to share, privacy.
Be able to control other apple devices like Macs, Airport Extreme, iPads, AppleTV, and use the watch as a remote.
I think think since the iwatch is paired to the Iphone, it would be nice to pair other Mac products, so that the iWatch can be used as a security mechanism. Instead if a lock screen or login screen, your phone or other device will wake up and unlock your device by sensing your hands proximity as a trigger. it is also a verification system by saying my device can't be unlocked inless I am wesring my watch.
Since the watch mostly depends on the phone for alot if the leg work, it would would be a good idea to not loose either. If an app can somehow be installed on the watch to not rely from my phone data, I would want to be able to find my iphone on my watch and find my watch on my iphone, that with an iPad would be cool.
Many times we dock our phone or ipad to a speaker, being able to change the volume of my phone, and control the music playing remotlry through the watch.
There is also a hood amount of "the internet of things" type of apps that come with a smartsomething device. Like a smart tv, the nest, door locks, security cameras. That app data can be pushed to the watch and link the watch as an extension if the extension eco system. So I want doors unlocking and locking to my proximity, lights in my living room to change based on my mood, lights turning off when i go to sleep, see who is ringing my door bell, garage to open automatically so we can get rid if garage remotes, and so forth.