I had a great idea the other day, to make a water bottle that would use UV LEDs to clean the water inside the bottle. After a little research I found someone who had a similar idea and did it very well.
From an Inhabitat post: While traveling through Zambia, Timothy Whitehead became perplexed with the issues surrounding purifying water — chlorine and iodine tablets abound, but it takes 30 minutes to finish the process and the water tastes terrible afterward. Enter his new invention, the Pure Water Bottle, which is capable of filtering soiled — completely gross and disgusting looking water — in 2 minutes flat. Whitehead used a combination of a 4 micron-sized water filter and a wind-up ultra violet light system to clean the water of 99.9% of its impurities.
