I'm planning to deploy an app on my android smartphone which is supposed to be used by multiple other persons. Now of course I do not want them to do things with the device they are not supposed to do so I informed myself about several different ways to make it as safe as possible (Lock-down apps, Kiosk mode, Mobile-device-management, Code-tweaks and so on).
I found some solutions that look really promising but they all share the same problem that a user could just restart the device and boot it in safe-mode where those helpful apps won't be started. However, there is one exception: I've installed a MDM app called maas360 which somehow manages to apply the restrictions that I defined even in safe-mode, for example by blocking access to the menu settings. How is that even possible? The thing is just that this is not a free app and it offers a huge variety of functions - overall it seems to be a bit excessive for my goals.
So my general question would be: is it somehow possible to restrict access to the safe-mode somehow? Maybe like a password? From what I understand it is not even possible to set a system password for Android devices that you'd have to enter once it boots (except if you set up a password for unlocking the screen first which would then be the same one... very redundant).