Anybody not doing it already, look at how the link to the binary is
formed, and contents of the plist file. This is the "enterprise"
build option, which any developer can do.
The downside of this is that people with jailbroken devices are simply
downloading and installing. Which is a mixed bag because they don't
use up a UDID, and they will often send bug reports. But fortunately,
not many people are willing to do this to a device.