I recently bought a SecurityMan ClearCam so that I can see who is at my front door when I am out back in the shop. The advertised range was 330ft clear line-of-sight. In my installation, the camera will have to beam its signal through walls, and the the distance will be about 150ft, so I thought I would be fine. The reception turned out to be pretty bad, so I added an antenna that is more directional than the included quarter-wave piece-of-wire antenna that comes with the unit.
I built a 3-element Yagi antenna that was designed for 910 MHz, which is what the camera claims to use.
I built a corresponding antenna on the receiver. This arrangement provided a helpful improvement, but the reception at 150ft through some walls is still not %100. Frustratingly, the image appears perfect, then suddenly degrades and goes completely black, then returns to perfect again every 10 seconds or so. I have no idea why this would happen. The 910MHz band was specifically chosen to avoid interference with 2.4GHz devices such as WiFi. Oh well, it seems to work well enough for my application.