Not effective unless you’re always able to see the bottle.
I should have read all the reviews, because others had mentioned this.  Unless you’re able to see the sensor when it blinks after 30-40 minutes this gadget is useless.  The rapid blinking repeats 10 times—maybe for about 45 seconds total—and then stops blinking. So unless you happen to see the sensor in that very short period of time, you have no reminder to drink more water.  Probably a great item if you’re at a desk all day, but don’t go to the restroom LOL.
Rating: 2 stars