That is pretty neat. I actually like those flip top lids. I have not seen the Nalgene bottles with those lids for sale in quite some time. I think they got complaints about them leaking, but they work very well in an external pocket while hiking where they just need to seal against splashes.

I wish that had a universal adapter that could cennect to the spout in the flip top lid and the Smart water bottle threads.

Another thing to consider is that technically any 3-d printed object is not food safe. The reason is that the manufactoring process creates lots of tine cracks and crevices that can grow bacteria. The Smart bottle cap doesn't have much contact with water so it might not be a problem. I didn't see anything where the guy seals the lids after printing. If he doesn't, you might want to do it yourself. I would recommend a food grade flowable liquid silicone.