Just sanity-checking a concept... poor man's self-monitored alarm system If I wanted to throw together a simple burglar-alarm system that had wireless sensors talking to an Arduino (which would then send me an SMS message via cellular shield as a silent alarm telling me which alarm sensor had changed state_)... what technology would you recommend for the sensor-to-arduino signalling? 

It needs to be something that draws little or no power until the alarm is triggered, resistant to radio interference, and as always cheap is a huge plus.... but I haven't gotten much beyond that.

(Of course if anyone's already implemented something like this and there are descriptions/sketches I can adopt and adapt, feel free to point me in the right direction.)

EDIT: To provide more info,this is a wood-framed house, 2 storey plus basement, brick chimney possibly in the way. No straight-line distances greater than 60 feet. Wifi, wireless phone, usual electronics and a wood shop I'm still putting together. Shouldn't be difficult, I just want a robust solution in case a friend asks me to replicate it... and for purely aesthetic reasons.
NRF24L01+ for communication. Extreme low power if not sending. Detects packet loss, and automatically resend the packet. 

You would however need a small arduino board at the sensor, to read the sensor, and signal to NRF24L01 to send a message. 

You'll have to put the arduino in to low power sleep mode to get some good battery life. Either have the sensor wake the arduino up with an interrupt, of poll the sensor like every half second, and immediately go back to sleep.