My first choice was to backup to DVD. I could only find 2 models: 1 by Sony (very expensive, mainly for backing up videos to DVD-video) and Plextor's PlexEasy. PlexEasy came out in Jan 2012 and isn't very popular, so I don't know how reliable it is. Also, all available stock seems old.
Second choice was a USB-to-USB copier, since SD cards are so cheap that I can buy extra. These are slightly more common, but they are usually 1-to-many, also expensive, and quite bulky. These are meant for copying USB drives for distribution. I even looked at using Arduino, but it's very slow - more than 30 minutes to copy 1 GB.
There are some devices with built-in harddisks (Epson made some quite popular ones), but, like the PlexEasy, they're old (not sure if they're still being made). Since they use harddisks, I don't really trust them.
I think the reason these devices are so rare now, is the popularity of tablets and smart phones. People can just backup onto them. I searched if this was possible with the iPhone, but everyone seemed to agree the camera connection kits only worked with the iPad. Even jailbreaking the iPhone didn't guarantee success. It seems possible to connect USB devices to Android (USB host or USB OTG), so that's my second choice, after my iPad.
I found another device: HyperDrive's iUSBport. What this does is take any USB mass storage (flash or even harddisks) and serves them over its own ad-hoc Wi-Fi network. It can also join infrastructure networks. It's battery powered, powerful enough to power harddisks. Around SGD149.
- Works with any USB Mass Storage device
- Works with any device with a web browser (iOS, Android)
- Can serve data to several users at once
- Can function as a charger?
- Has a screen
- Does it have a "copy/select all" function, if I want to back up photos? I'm not going to open each photo and save them individually.
- Only some video file types can be directly played in the browser. Otherwise you'll need another app
- Doesn't have an iPhone app yet (only iPad)
HyperDrive also has a device with a built-in HDD, like those Epson devices I was talking about above. It's the ColorSpace UDMA. The nice thing is, it seems to include all iUSBport's functions (i.e. it can serve files over its self-generated Wi-Fi network), in addition to a screen and its own storage. It also has some unique functions like CRC error checking and file recovery. I like how all HyperDrive's products seem to be firmware upgradeable.
Alternatives: Raspberry Pi? I'm sure it can copy things between USB ports, it's just a matter of writing a script to do it without a keyboard and display. If possible, it would be really cheap too ($50).
Update 22 Jul 13
I found a similar product to the iUSBport by the company Apotop, called the Wi-Reader (DW09). It has a USB and SD card slot, and can definitely function as a charger. This one even has an iPhone app.
Update 23 Jul 13
SanDisk has just announced 2 such devices: SanDisk Connect Wireless Flash Drive (stores on microSD) and SanDisk Connect Wireless Media Drive (has internal storage and SD slot). I guess if you use a microSD card in your camera, you can use the Flash Drive, if you use SD cards you can use the Media Drive, and the Media Drive has its own memory to back up onto.
Update 24 Jul 13
Found yet another device, FileHub by RAVPower. Like the iUSBport, it has a USB port and it also SD card slot. It can even use both at the same time and directly copy things from SD to USB. It can be used as a battery. If you look at this on Amazon, there are other similar devices in the recommendations.