Looks well made. It looks like a "belly band" style, just for higher up.
The only problem with under the shirt carry is getting to your weapon. The grip looks like it will be in your armpit, so drawing straight up and out of the holster will be tough. Not to mention getting to the gun. You'll have to practically take your shirt off.
Rule of thumb is that from a normal standing position, you should be able to draw and fire accurately at a target in 1.5 seconds. That's why most concealed carry folks carry IWB.
That being said, with enough practice, you could probably drawn from anywhere in a second and half. And having a gun with you is better than leaving it at home.