Non-substantial remote door locking options for indoor rooms?
If you do find a solution that works for you make 100% sure that it is possible to enter or leave the rooms even when they are locked. In the case of fire or other emergency situation the last thing you need is inability to escape or enter the room to save someone. You need to consider that the power in such situation may be off, rescue personnel will not be familiar with whatever gadgets you have rigged up and in the frenzy of the situation trying to locate remote controls may not be feasible.

It will always be best if such access capability is entirely mechanical and localized right at each door unit. No dependency on power, remote tools or non-standard operation.