Today I have received this new product from Apotop:
Despite looks like a card reader, this device is not so simple. On the back there is an ethernet port since can work like a hot-spot WiFi up to 5 devices. On the front there is SD slot with USB 2.0 space, that with WiFi enable turn the device in a WiFi storage solution. Inside this little device, there is a 5200mAH battery that should last for at least 14 hours. This same battery can also be used as a power bank to charge other devices, and it supports Fast Charge mode.
I have already downloaded the free app for my MotoG but there is one even for Apple.