Conectivity plays a huge role in the way we control our camera
The CamRanger is a standalone device that connects to select Canon or Nikon DSLRs to create an ad-hoc Wi-fi network, which mobile devices such as smartphones and tablets can then be connected to. The CamRanger app (available as a free download) offers full wireless control of the camera, with advanced functionality such as toggling between Live View, adjusting key imaging variables and viewing full resolution images. If you're looking for a wireless tethering solution offering great control of your DSLR, the CamRanger is well worth a look, but not cheap at £269.
Cable releases or smart triggers are very useful for triggering your shutter when you don't want to come into physical contact with the camera. While cable releases can be great for long exposure photography when working close to the camera, they're more restrictive if you'd like to work from greater distances. This is where Smart Triggers come in and accessories like the WeyeFeye enables wireless and remote access to the camera shutter and settings via an app.
3 GPS Unit
If you'd like to embed co-ordinate data to your image files, such as the latitude, longitude and altitude of your location you'll want your camera to support GPS. Whereas some cameras feature GPS built-in as standard, others require a small GPS unit that attaches to the camera via the hotshoe, with power supplied directly from the camera.
4 PC Sync Adaptor
If your camera doesn't feature a built-in PC sync terminal and you'd like to trigger flash via a sync cable you'll require a PC Sync adaptor that's designed to attach to your camera via the hotshoe.