I need help in finding the best approach towards a stealth project. I am operating a mission in my home where I need to ensure that I cannot get flanked / approached by someone from behind and not notice. Basically I will need to construct a couple of motion detectors that:
1) Are reliable and won't trigger randomly.
2) Are very small and easy to deploy.
3) Aren't expensive, so if they get destroyed or lost it wouldn't be the end of the world.
4) Work in the dark.
5) Are able to send a message / notification to a device REMOTELY. I can't use anything that makes a noise like buzzers etc.
I've thought of trying to interface an RF system where as soon as the motion sensor detects motion, it uses a connected RF transmitter and sends a signal. But how would I interpret the RF message, and on what device?
A second idea that came to me which I think is more realistic is to set up a raspberry pi server, hosting a simple webpage on my home network. I could then use an esp8266 Wi-Fi board together with a small arduino and motion sensor to send a packet of data to the webserver whenever the motion detector is triggered. I would be connected to my home network from my mobile and be viewing the page, so I will get informed whenever there is motion detected.
What are your thoughts about the potential solutions I have described? Are there any alternative methods that I should consider?