It's all about the power
Power is key.
Plug your iPhone into your iPad
This one came as a tip on a previous article – thanks Aaron! – and it works just great. It actually mentions doing this somewhere in the paperwork that comes in the box with the connector. So if you don't read the paperwork – guilty as charged – then you maybe wouldn't know about it.
USB microphones will work, well, some of them
I was a little surprised by this one, I have to say. Again, power is the issue here, not the fact that it's a microphone. For example, the little travel microphone I have that's pictured here – a Samson GoMic – works just fine, while the honking great Rode Podcaster we use to record our podcasts most definitely doesn't.
USB flash drives
As mentioned above, USB flash drives do work to an extent. But, they seem to be recognized only as a camera would be, for importing photos. Pre-loaded .mp4 video files weren't recognized in my tests, so there's no scope to import videos to your iPad in this way it seems.
So, those are a few things I've had lying around to test out with the Apple Lightning to USB Camera Adapter. If you've had experience with one though and have had success with using it to plug things in to your iPhone or iPad, drop a line in the comments and share your experience with us!
There is an article about how to use external web camera, please watch it together. If you have any questions, remember to reply.