I suppose metal plate, or brick, or even heavy plywood, in the associated walls will be helpful too. Nothing perfect, but with intruders in a hurry they may not want to take the time to bust through walls.
Speaking of walls. I have a bunch of cheap glue-on mirrors at the end of the hallway that leads to all of our bedrooms. More and more I’m tempted to change some/all of them to two-way mirrors (with mods to the wall of course) so I can be in the master-bedroom closet looking out the mirrors into the hallway in case of a home-invasion. I guess if I really thought it out I could reinforce the lower portion of it with steel & sand. Although I imagine sending numerous rounds down the hall through the mirrors would surprise any intruders and they wouldn’t be able to react fast enough.
Home invasions are pretty rare in my area, but I imagine they will be on the uptick. (And of course, it only takes one.)