I carry an iPhone, at least $100 cash, a book to read, and a USB battery that can recharge my iPhone completely, twice.
Teacher, what battery do you have that can charge an iPhone twice? I've been searching but haven't found anything.
Not to mention my laptop, which is almost always fully charged
My laptop is one of the first things I would ditch if I had to travel any distance. In an emergency, a laptop is 6 to 8 pounds of relatively useless plastic and silicon. Time permitting, I would pull the hard drive and take it with me, but no loss if I have to leave it behind. The disk is fully encrypted (McAfee Safeboot) and automatically backed-up each time I connect to a network (Carbonite). The ability to use it to charge my phone doesn't justify the weight and bulk IMHO.