Ocean Technology via Amazon offers Prime members the Unitek Detachable 4-Port USB Charging Station Dock, model no. Y-2187A, for $29.99. Coupon code "2E3KDYEE" drops it to $15.89. Plus, Prime members bag free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $7.15.) That's $44 off list and the lowest total price we could find. It charges up to four devices at once, and is compatible with iOS or Android devices.