I've tried to do some research to figure this out, and per this Technical Q&A:
USB Prober is installed as part of the Developer SDK installation. If the Developer SDK has been installed, then locate USB Prober at /Developer/Applications/Utilities/USB Prober.
I'm on Mavericks 10.9 and don't have a /Developer/Applications/Utilities folder.
My IOS Simulator is located here:
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/Applications/
So I searched in all of the subfolders of /Applications/Xcode.app/Contents/Developer/ and even /Applications/Xcode.app/ but didn't find anything with a name like USB Prober.app
I don't see anything in the downloads section of Xcode:

