Meet the H2OPal: an automatic hydration tracker that pairs with your smartphone or Apple Watch to help you stay hydrated. It automatically tracks your water intake and syncs with your smartphone. The device sends you reminders when you are not drinking enough water.
H2OPal is a thin device at the base of the bottle. It does not come in contact with your water and runs on a coin cell battery for months. Costs under $100 at this time.[where to get it]