How can I set up a motion sensor that makes a soft alarm go off in another room when motion is detected?

I want to put a sensor in the corridor, so when someone walks past it makes a quiet beep of buzz in my bedroom so I know to turn off the tv and do homework. Could someone please tell me how I could set something like this up?How can I set up a motion sensor that makes a soft alarm go off in another room when motion is detected?There's a readymade product for this - see the link. The sensor isn't particularly small, though.



p.s. You should be doing your homework anyway.How can I set up a motion sensor that makes a soft alarm go off in another room when motion is detected?if u like build the circuits by ur self then try this

http://www.circuitstoday.com/infrared-mo鈥?/a>