I always have had somewhat of an unrealistic dream of taking an Apple Watch, removing the screen completely and installing a super thin mechanical movement on top (or putting the guts into a more tranditional looking case). I think it would be possible to use a smaller battery once the screen isn't there, to make more room for the movement as well. I'd love to have the health tracking features, and while I don't have an Apple Watch, I think that it would work without a screen and I'd just be able to use a phone to see the data.