Groupon offers the AdNArt Beat Bottle for iPhone in Red, Green, or Blue for $13.99 plus $2.99 for shipping. That's the lowest total price we could find by $18. This 18-oz. water bottle stores and amplifies your iPhone, and features a wrist strap and flip spout. It's compatible with iPhone 4 or 5. Deal ends July 30 at 1 am ET.