Glass microblocks specifically won't work. I don't know if this is what you want, but you can use a jacketed wire to send signals without having to put the wire on anything. So instead of a wire running up a glass window, it will be in front/behind it.[DOUBLEPOST=1361101569][/DOUBLEPOST]I did some tests in creative, and red wire can actually be placed on warded glass.
Mob spawners, soul cages (even empty) and iron tank gauges can also support red wire and are see-through.
Glass, stained glass, reinforced glass, hardened glass, ice, or beacon blocks didn't work.