There are potential other solutions, but none I know of as straightforward and convenient as ReadyCloud. Most start with having to set up a VPN, which ReadyCloud does for you.
The one potentially more convenient would be if you already have a "smart home" and can put a remotely powered switch between the outlet and a UPS. But the shut-down wouldn't be immediate -- it would have to wait for the battery to get low.
Another way would be using remote software (TeamViewer, GoToMyPC, etc.) to access a PC on the same network and accessing the NAS GUI via that computer. But I wouldn't consider that more convenient, especially from a smart phone rather than another PC.
