Install wiringPi https://projects.drogon.net/raspberry-pi/wiringpi/download-and-install/ -> sudo apt-get update && sudo apt-get install git-core && git clone git://github.com/kennethreitz/requests.git && cd requests && sudo python setup.py install && cd ..

Get 433utils: git clone git://github.com/ninjablocks/433Utils.git && cd 433Utils/RPi_utils && rm RFSniffer.cpp && wget https://raw.githubusercontent.com/Astu04/Raspi_PIR_Push_notif/master/RFSniffer.cpp && nano RFSniffer.cpp // We now modify the value in this file: Remember that value for step 6. // sudo make && mv RFSniffer /var/www/

if (value == 12345) { // <--- The number

sudo apt-get update && sudo apt-get install urlwatch lighttpd && sudo urlwatch

Now we create a file /root/.urlwatch/urls.txt with: http://localhost/log.txt

$ echo 'http://localhost/log.txt' > /root/.urlwatch/urls.txt

Wire everything up (See tutorials in 433utils/wiringPi) tl;dr data to pin 2, and then vcc and gnd.

Sign in http://pushetta.com/ , create a channel, go to dashboard and get the API key. Install the app on your compatible device ( See list in http://pushetta.com/pushetta-downloads/ ). Subscribe to the channel you just created. Modify the .py file with the API KEY and the channel name. My channel is "Stairs PIR".

Modify and upload the .ino to the ATMEGA328 following this tutorial: https://www.arduino.cc/en/Tutorial/ArduinoToBreadboard

Move all the files (.py, .sh, RFSniffer) to /var/www/ and write in the console ./RFSniffer

As homework, move all but log.txt out of /var/www/, so it isn't visible. You could also password protect log.txt

My ATMEGA328P-PU consumption keeps at 90uA most of the time, so a battery should last a long time. The PIR sensor I picked drains by itself 50uA.