One-time key stash

I need to hide my key for emergency use.
Because I afraid 'smart lock'(retrofit) is not smart.

Requirements
- It can reveal that someone found and touch it
- You have to break it to get the key and it's hard to recover
- It can withstands rain and protect key from humidity

Solution
- When removed, a magnet inside will fall down and appear in the window
- You can break it with bare hands to get the key(like a piggy bank)

With functions of the smart lock, I can check status history of the lock even in real time.
With this thing, now I will never meet the thief or robbery unexpectedly in my house.
Of course, need not afraid rebellion of HAL-9000.

We also recommend adding some secret gimmicks to increase your security level.

Additional information
You need get some stuff to make this thing.
1. x3 magnet diameter:13mm thickness:2.5mm
2. magnet sheet (thickness: less than 1.0mm)
3. masking tape for sealing gap
4. some fluorescent paint




How