"the carriers and phone makers are all REQUIRED by calea (in the US) to have backdoors on anything that has a 'network' aspect to it."
"they have magic usb cables that get into your phone"
I think I saw a website of a company that claims to have such a device, but I had the distinct impression that it mostly helps with booting into recovery mode (android phones); it will tell you which combo of power/volume up/down to press during boot. Some phones don't have a locked bootloader or have a bootloader that allows installing software to the "ROM" from the bootloader. (I've seen this on low-end Samsungs and the popular Clockworkmod bootloader for Cyanogenmod allows this).
For phones that are switched on, it will.check for usb debugging and mass storage access.
Essentially, it has collected the known procedures for rooting for a lot of phones. Guess what, a lot of phones cannot be rooted without either having unlocked the screen or wiping all user data.