The hardware wallet itself is not the main thing I would worry about in a crowded house. Someone finding or even stealing the device does not automatically give them the Bitcoin; the recovery backup is far more important. I would keep the hardware wallet and recovery backup in separate, discreet locations and avoid telling people where either one is kept. An alarm can provide an extra layer of awareness, but it does not solve the main problem if the seed is exposed. For larger holdings, a properly managed passphrase or multisig setup can also reduce the risk of a single backup being enough to access everything. Privacy is probably the simplest security layer here.

Instead of setting up an alarm system in the locked safe that will notify your friend, don’t you think it’s better your friend looks for a better place to keep the wallet, it’s just better your friend keeps in a place where nobody can access it, a place where nobody knows that something like this can be stored there.

If your friend set up an alarm system in the locked safe, and he receives notification on his phone, what if the safe is Broken when he isn’t around, even if he receives notification during that period, what is he going to do? He won’t be able to arrest the person that broke the safe, because he doesn’t even know who did that, and he won’t be able to stop the person from breaking the safe because he isn’t around.

There should be at least some privacy, and if you aren't getting some privacy it means that they don't respect you, if that's the case what are you still doing there? You should leave and find a privacy space.

I have live with families before and most of the times they don't touch my stuffs unless they ask for permission and I permit them, there should be some sense of honoring eachother.

In my case, if I live with a large family to keep my Bitcoin wallet safe, I will keep my hardware wallet in a locker. The key to that locker will be with me only, no one else will have this key except me, in that case, my hardware wallet will be very safe and should be kept in a place where no one knows it. Although it is often seen that if I live with a large family, at that time the family members may search for various things, if they find the wallet there, they may consider it unnecessary and throw it away. So you have to protect yourself. If you want to invest in Bitcoin and keep your money safe, then you have to create a safe place in your room where no one can enter except yourself. However, if you live with a large family, sometimes some things are not safe there, many people want to use them. However, if I invest in Bitcoin with a large family, my thinking will definitely be different and I will definitely create a safe place to keep my money safe.