PricePlunge offers the Eton BoostTurbine 1000mAh Hand-Powered Battery Pack, model no. NBOTO1000B, for $15.99. Coupon code "SPRING5PLUNGE" drops it to $15.19. With $2.99 for shipping, that's the lowest total price we could find by $7. This battery backup features a standard USB port and a hand crank. One minute of hand cranking produces enough power for about four minutes of talk time. Deal ends May 22.