If you're using Filevault for full disk encryption you can't have Prey installed and use it on an open guest account. You can have a guest account and use the i

If you're using Filevault for full disk encryption you can't have Prey installed and use it on an open guest account. You can have a guest account and use the iCloud 'Find My Mac' though. But that's exactly what I did on my last Mac (which wasn't using Filevault).