"but has a limit of 500 mA which, while it is faster than a USB port of your computer, it has four times less power than the cable can get from a wall socket (nearly 2 A)." Not quite - most computer USB 2.0 ports are exactly 500mA. Phones tend to pull 1A from wall chargers, and tablets 2A. (USB 3.0 is 900mA, but I haven't seen any phones or tablets that support it. In fact, my phone only pulls 500mA when plugged into a computer even if 900mA is available, yet it pulls 1A from a charger.) (Earth to toms: PLEASE fix the issue with line breaks causing generic errors...)