[Tom Givens]

A company called A Better Holster makes a compression fit T-Shirt undergarment with an elastic holster sewn under one arm, and magazine pouches under the other. From their website, abetterholster.com :
Concealment Shirt Holster ™
The Concealment Shirt Holster is an innovative and unique solution to your deep concealment needs. It starts with a moisture wicking compression shirt that pulls the sweat away from your skin and moves it to the surface to evaporate. It features a custom designed holster, which will accommodate most small to large frame handguns and a triple magazine carrier. It is available for both right-handed and left-handed shooters.

This shirt is similar in concept to the Kramer Confidant, and is available in black or white.

5.11 offers a new shirt called the Covert Carry Shirt, which is a nice looking sport shirt designed to be worn with the tail out, in one preferred carry mode. All but one of the buttons on the front are dummies, with hidden snaps behind them. The side vents are split, but closed with velcro. A mesh lining in the waist area breaks up printing of a belt holstered gun. Available in several colors.

I spent the weekend in an NPE, so I decided to experiment. I wore the undershirt holster, with a Kahr TP9 in it, under the 5.11 Covert shirt. I spent a total of about 12 hours in the presence of uniformed security, plain clothes security, and uniformed deputies. None approached me, or showed any interest in me, so I'd say it worked. This was in a city away from home base, so it wasn't a matter of knowing me. In a mirror, I couldn't see the gun, either. Toward the end of the 12 hour period, the gun started getting a bit uncomfortable, but that was probably because I never wear a gun in shoulder holster position except for this experiment. I would probably get used to it in short order if my life-style demanded this level of concealment on a constant basis.

In a casual clothing environment, I think this would be a viable carry mode. I was able to pop open the 5.11 shirt snaps and access the pistol pretty quickly, with minimal practice. I have also worn the 5.11 shirt with my G35, IWB and gone un-noticed in a less strict NPE. (NPE= Non-permissive environment, no guns)