Shit that really sucks !
It's actually one of my fear, because even though I do not have much that are actually valuables, some may seem that way and I know that if some of my books were stolen, I would not be able to afford or find replacement copies.
I always worry that my balcony may be accessible, allowing to break into my flat.
I don't know if anyone else has any similar "protections", but I personnally have bought a NEST camera and installed it at home.
The idea being that, hopefully, if someone tries to break my window, the sound will be picked up by the camera, giving me an instant notification and allowing me to have video footage for the cops, but also and mostly allowing me to call immediately the cops.
But then, if / when it would happen, it probably woudnt work