No I am not making this up, and I have not gone off the deep end.
U.K.-based New Scientist magazine's online tech editor Tom Simonite reports that Cambridge University computer security researcher Markus Kuhn has developed a way for a radio antenna and radio receiver to grab images off a computer screen through physical barriers.
In fact, the image you see at the top of this post was taken through two intermediate offices and three plasterboard walls.
What does this have to do with IM or VoIP?
Well, it seems to me that such a system could cut through walls to read your PC-based IM exchange. While actual voice calls would not be intercepted by this system, this set-up could also peek to take pictures of an IM or softphone-based interface- and then see what number you were talking to someone at.
And no, we aren't talking superspook gear here. The price of this setup is less than £1000 -about $2,000 U.S.
While that isn't a hugely overpriced amount, it isn't an insurmountable figure for the curious, mischievious, or worse.