I have been playing with some housing ideas for the sensor head that might work on the layout without looking too "clunky". Here are some pix of one idea. This is actually the large relay cabinet in the Lionel trackside accessory collection. I placed it on a convenient chunk of 1 x 2 just to get to the height needed for the sensor ports. To the right is a pic of the sensor head mounted in the cabinet with holes drilled in the back which would be aimed across the tracks. So the whole thing is pretty unobtrusive.
Here is the finished cabinet with the sensor installed, ready for layout trials. Only trouble is I need to build up another train detector board first because the two I built so far have the sensor soldered into the board! Oh well.
Note that going this route would be a bit pricy as the Lionel trackside kit seems to sell for up to about $30. Kind of crazy for 4 or 5 simple little plastic doodads that don't do anything except sit on the layout, but hey. One idea I am exploring is getting a 3D printer file together for something similar to this. I have a sketch made up that will fit these sensor heads really well, and it is higher so you don't need the wooden block under it. That would allow one to print up half a dozen or however many you need pretty inexpensively.
Research continues. 
Rod
