Amazon offers its Prime members the AdNArt Beat Bottle for iPhone in Red for $16.55 with free shipping. (Non-members can spend $35 or more to get free shipping; otherwise shipping adds $5.74.) That's the lowest total price we could find by $11, outside of the price below. This water bottle stores an iPhone and amplified the music played on that phone.

A close price: Groupon offers these bottles in Red, Green, and Blue for $13.99 plus $2.99 for shipping.