Just a suggestion, but you can always find some cheap 802.11b access points on ebay that are dirty cheap. Put one of these in the rafters of your garage, or even put a larger antenna on it and you would be surprised the distance you can get.
or you can do like I did. I put a repeater in an enclosure and mounted it under my deck. Then ran the network cable back to my switch with a POE injector so I didn't have to worry about power. Mounted it under the deck so it's not seen. I have almost 2 acres and there isn't a spot where I dont get at least 3/4 bars on my ipod touch.
Not really what your looking for, but it would solve what your wanting to do, plus more.