Amazon offers its Amazon Prime members the Belkin Fast Fit Armband for iPhone 4, model no. F8Z611tt, for $7.99 with free shipping. (Non-members can spend $25 or more for free shipping; otherwise, shipping adds $5.17.) That's the lowest total price we could find by $15. Features include a cable capsule for keeping headphone cords organized, water resistance, adjustable fit, and more.

Note: Amazon states it should ship in three to five weeks.