If you want a quick and efficient way to carry your XD-S IWB or clipped to your pocket, I highly recommend the "ClipDraw" Universal! It is extremely versatile and easy to install. The one I currently have on my XD-S was used on a full sized 1911, a Glock 19, a Kel-Tec PF9 and Lastly, on my Ruger LCP before I installed a side mounted laser on it. The "ClipDraw" universal in no way prevents the gun from being holstered. It serves very well for a quick way to carry the gun when going out and you don't have time to put on a holster or you don't want a holster. Here is a picture of the gun with it installed: You can check out their web site for further details here:http://www.clipdraw.com/
I have no problems wearing the gun iwb with only the clipdraw..between the underwear and your pants! Not against bare skin though. As I said I would wear it this way for a quick jaunt to the store, etc., but for all day I would holster it. You can also clip it to your belt between the belt and the pants if you so chose if you are wearing cover garments to conceal it. I have a clip draw made specific to Glock that I have on a G27. I wear it and have worn it many times IWB for several hours without and problems. It actually conceals much better as it is thinner than wearing a holster.
You get a trigger block like this. Your finger pushes it out of the way when you need to shoot your gun. I have one for my glock 27. I am currently in contact with ClipDraw to see if they make or can make a trigger block for the XD-S
