Thats what this app is all about. Reminds you at preset intervals to have some water thereby helping your body expel unwanted toxins.
Some additional features based on consumption patterns might be even more helpful.
Update as of 15 October:
Recent update caused app to crash on load. Even the latest bug fixer update didnt fix the issue for iOS 6.1.3
Vishw4ever about Drink Water PRO Daily Reminder