Power Bank, Vinsic 20000mAh Ultra-slim Power Bank, 10 Times for iPhone 5S, Dual USB Port 2.1a 1a External Mobile Battery Charger Pack for iPhone,iPad,Samsung Galaxy,Cell Phones,Tablets. Vinsic http://www.amazon.com/dp/B00M6VA7OU/ref=cm_sw_r_pi_dp_Spj2vb02YV05P
One of these would help with the most difficult part of being in my car so much. My battery mysteriously dies regularly, in part because I forget to remove the USB charger from the cigarette lighter. Multifunctionality makes many of items and this review especially appealing.