The Galco horsehide pocket holster for j-frames is good, but with any pocket holster it has to fit the pocket or be retained during the draw unless you intend to draw the gun with the holster on it and then remove the holster. The Galco, like a lot of pocket holsters is sort of approximated on a front jeans pocket, that being the most common type. A chest pocket is a little harder to imagine exactly how it will work. Depending on how you get a grip and make the draw, the orientation of the holster and how it is retained in the pocket would have to be worked out and depending on the size and shape of the pocket, you might need to mount the holster on a panel that is better retained in the pocket.
BTW, I've had a Sticky, the Desantis Nemesis, a Crimson Trace pocket holster that is neoprene foam, and two Galcos, the "pocket protector" and "horsehide." I've used them with several different j-frames including the 340 PD.
So I've had some experience with this, and while I think the horsehide is the best of the pocket holsters I've tried, the key thing with pocket holsters is the fit to the pocket and retention of the holster to the pocket when drawing and this has less to do with the holster itself, and more to do with how well you customize the fit by either fitting a panel to the holster or stitching the pocket so the holster is retained.
It might not be good for running, but I also have the Galco ankle glove. That one works very well for the 340 PD.