I've been using Prey for a while now. Today I wanted to log in and check on my devices settings. As I had forgotten my password I reset it and got into the Web panel normally. Checked my settings there and disabled Camouflage mode for my phone (Sony Xperia Z5 running Android 7.1.1). I opened the Prey app on the phone, logged in and saw that the Shield OFF option was deactivated and it could now only be activated by entering a PIN beforehand (before, no PIN was needed for this function).
In my opinion the PIN function doesn't add anything to my security but adds inconvenience, personally. I'd rather have no PIN as I already use a complex pattern lock and finger print.
Suggestion: make PIN on Power Menu in Lock Screen optional, but add a feature that silently takes a picture with the front camera when trying to use the power menu on the lock screen, ideally sending it to my email address.