Andy, the WD drive has an app that allows you to access media on it remotely. As I stay away in hotels 3/4 nights a week on average it’s great to be able to watch movies, box sets etc. I find it works really well on wifi (and unlike sky, iplayer etc it doesn’t get confused by hotel wifi that thinks it’s in France, Belgium etc). On 3G on the ipad it works ok but it eats bucket loads of data if watching a movie. It doesn’t struggle with three devices steaming different stuff at the same time.
They also have a dedicated photo app that I can use to take pics and they auto upload to the hard drive, or use to view them. We use it to turn an ipad into a digital photo frame sometimes.
I can’t remember how much I paid but it wasn’t expensive, which is why I bought a 2TB drive to give me a bit of future proofing.
It sits next to the wifi router at home, but can sit anywhere with a power socket, and acts as a wireless network drive you’re right.