Hi,
This is not such a big deal. You can use an IR sensor to sense any intrusion and send a warning message or call to a predefined mobile number.
But there are certain things which you should consider.
Basically your project should work 24*7 without any failure. Continuous power supply, stability of the controller which you choose, and the stability of the code, sensor performance etc. will be having significant effect. There should not be false triggering also.
What you meant by that “Chinese bug”? Is that any hardware?
Anyway, choose a MCU, GSM module, sensor which you like. Design the sensing circuit first. Then try to interface the GSM module. There are lot of examples for GSM interfacing in engineers garage, which I hope you’ve already found.
You can start the project and update your doubts here. Surely you will get a lot of help.
All the best