RIFD / WIFI locator?

Does anyone know a system or how to construct an RFID / WIFI based locator system?

I would think that an old dual antenna wireless G router could be used in combination with an RFID tag.  So when the tag is moved to a new location within range of the router the location will be saved or displayed on the computer screen.  

I thought that having a system like this would be great for keys, animals, phones, babies, pills, etc.  

Here is one example application:

Where are my keys?  - open the web browser and retrieve the approximate location where the keys were last moved.  They are in between the sofa cushions. 




Most RFID systems are short ranged. Those that are long range either have a rather large reader or use and active RFID tag. But neither RFID or Wi-Fi are able to track location. Best you could get out of either tech would be a direction. But the tag would have to be actively broadcasting a signal.

Your best solution here is an existing key finder system like this one. Push the button on the remote and the tag on the keys sound an alarm.

http://www.eachbuyer.com/4-in-1-wireless-lost-key-...