In-wall or on-wall beam antennas.
I went to a presentation for the NUTS Cubesat ( http://nuts.cubesat.no
) where one of the presentations was about implementing UHF phasing networks and transmission lines on printed circuit boards, and I've also seen Yagi-Uda beams implemented on PCB style boards ( http://www.wa5vjb.com/products2.html
This reminded me of an idea I had this summer: What if I hang some wires in a beam antenna pattern, on a wood wall that is perpendicular to a hard-to hit repeater, would it make a workable stealth vertical beam? The house in question has only wood sidings, the downspouts are PVC and I'd stay away from wiring. Has anyone tried this out? I tried searching online, but I can't seem to have found the right keywords.
Hiding a beam antenna in the attic is complicated by the presence of protected bats, and the metal roof material.
Stealth isn't really a requirement at my location - it's easy to get permission for antennas if needed - but it struck me as an obvious solution that I haven't found any examples of online. You'd just hang some wires next to each other on a wall, be it on the exterior or interior wall.