The Suspected Fly on the Wall was a Horse

 Not a horse-fly, a real horse. 
 My friend and colleague, Tim Johnson, relates the tail tale...

"I was contacted to do a debugging sweep of a company executive area and an executive residence in a midwestern state. Having concluded the examination of the offices without finding anything I proceeded to the residence where I repeated the process. 

During the radio frequency examination I detected a radio frequency that I noted for additional analysis. In doing a further examination of the signal it was determined to be originating from outside the residence. This was done by moving my receiver to different locations and checking the signal strength. 

There was a barn located in the general direction of the signal path so I went out and did a further check." (more)

(Foal Alert Transmitter)