Radio or wi-fi motion detector

I would like to build (from easily available materials) an outside motion detector that would alarm if anyone came  into my carport at night. Battery powered (do not want to have to do house wiring), motion or ir sensitive (whichever gives range), sits somewhere outside in carport and  when activated broadcasts signal to turn on buzzer or other warning device in house bedroom, 100 ft or so away from detector.

I do have an available electrical plug in the carport so I could use that for power instead of batteries if needs be.

Does this stimulate anyone's creative juices?

Thanks 

Does your car port have a light or is there and outside light on the side of your house that faces the car port? If so you can buy a motion sensing light fixture. So any time someone walks near it the light turns on. That will scare away any would be intruder and be a convenient way to light up the car port at night. Best of all it gives you most of what you need to create the alarm you want. You should be able to open up the sensor and see how it works. From there you could wire it up to an Arduino and Xbee transmitter. It can be configured to report directly to your in home wifi network or have another arduino with an xbee to receive the signal and perform whatever kind of flashing lights and/or alarms you want to go off when someone get near.