On OS X there is a tool called ioreg that lets you dump out the contents of your I/O Kit registry. On OS X and iOS the I/O Registry contains a wealth of information about the hardware connected to your device. If you want to write device drivers then you’d have to get your hands dirty with IOKit. If you fancy some bedtime reading there is more information here.
I thought it would be interesting to see what I could get out of IOKit on iOS. Fortunately, Apple provide the source to ioreg. So I made a little iOS app based around it. Of course, IOKit is a private API on iOS and our app will be running inside of the Sandbox. That said, there is a wealth of information available. You can drill down into the I/O Registry tree and you can search too. It’s pretty quick and dirty and looks like this:
You can grab the source on github