Wireless communication

Hi Everyone, My home has a bunch of french windows with sliding doors, and I'm trying to come up with a way to secure them. This is what I've thought of so far: - Each door has a sensor with a reed switch that can dell whether the door is open or closed - The sensor can send its status (ie, open or closed) over some sort of wireless link - An Arduino receives these messages and displays the status of each on an LCD, and has some programming to handle alarms etc.

I'm looking for advice on what options I have for the wireless part of the project: all my Google searches keep bringing me back to XBee, but I think that may be overkill for such a simple use? I've also found these http://www.sparkfun.com/products/8945, but the site says you can have only one per location, which rules it out for me, since I'll need one per sensor. I'm trying to keep the costs down to about USD 20-25 per sensor, and they'll also need to be low-power. Any suggestions or advice is much appreciated.

Read the comments on that sparkfun transmitter - they point out (of course) that multiple transmitters cannot transmit at the same time and expect to get read successfully. For your application, that would not matter.

There are more sophisticated cheap ISM RF modules available like the RFM12 for which there is library support - you might want to look at how JeeLabs www.jeelabs.com.

@wildbill: yes, you're right, I could probably have the transmitters retransmit at randomized intervals and make the Arduino handle collisions. @markt: the jeelabs units look good, I'll see if I can get my hands on them.

Thanks for all the help.