These adapters plug into the USB port on your DSLR, and create a wireless network – similar to those generated by the microSD adapters – which you can access from a phone, tablet, or laptop.
But unlike microSD adapters, you can set them up to automatically sync pictures, as they're taken, with any devices in range of the Wi-Fi network.
Unfortunately, they only work with Nikon and Canon DSLRs. They're expensive, too: the Camranger is around $300/£200/AU$400, while the HyperDrive iUSBportCAMERA2 (opens in new tab) is $270 (around £180/AU$385).
Nikon has had its own stab at this market: it's £65 dongle (around $95/AU$135) is more affordable, but it only works with mobile phones, and not with tablets, laptops, PCs or Macs.