I have a small iPhone, limited data, and a loooong commute. I got this to put music on and stream through my iPhone in my car.
This is a wifi-enabled memory stick. It has a battery that can broadcast its wifi-signal for 2 hours with one device connected, presumably it lasts less with more devices connected, up to 5 I'm told. You can also plug it into USB charging ports in your car. This is just local wifi, so no internet.
I plugged it into my computer to set it up. I gave it a network password and moved my music onto it, but you can put anything on it. Anyone with the password and a wifi-enabled device can access the drive, and if they have the SanDisk app, they can use their phone to see anything on it. And that's the only weakness to this idea.
The SanDisk app is a very limited playback device. Playlists don't work for it, so you have to manually build music folders. The device won't stream through itunes on your phone, or any other media player. However, if you're on a computer, you can just access the files like you would on any other network drive.
This would be the perfect device if the app could play playlists, or you could stream through any app on your phone, not just the SanDisk one.