App to lock my iPhone for some time
I'm from the Flipd team and just wanted to chime in here. The MDM used to activate the Full Lock in order to hide your apps is completely safe. Not only does Apple thoroughly vet apps like ours that use MDM, the call we make via MDM is only to hide your third-party apps and then to push them back onto your device over the internet at a scheduled time. This feature is similar to Apple's Restrictions mode, but on a schedule. 

The only error you might run into is if you have a weak or no internet connection; at which point your apps may not appear as scheduled. This is easily resolved by uninstalling the MDM and your apps will return immediately. 

I hope this helps!