Does such a thing exist? I'm thinking of having something set up for when we go on hols, I'd like it wireless upnp to access films and music to Android tablets, a decent sized hard drive (or memory card) to host the files, but it needs to be USB powered for transport.

I do have a raspberry pi, could it be set up as a wireless access point?

I have yet to find a WiFi nas but have a look at this. http://www.ebay.co.uk/itm/Measy-R2W-150M-Mini-Wireless-Travel-Router-150Mbps-WiFi-NAS-USB-3G-Hotel-Office-/291137991486?pt=LH_DefaultDomain_3&hash =item43c92d333e

[Edited on 1/4/15 by britishtrident]

Aha, a travel router with USB support, that's what I was after! Not too keen on the overseas shipping, but it took me about thirty seconds to find an onshore equivalent for the same price so thank you for putting me on the right track.