I've been wearing a haramaki everyday for two months. The fashionistas among my readers already know that this ancient Samurai undergarment is fast becoming a must have. Here is the Wiki page.
I can think of no other article of clothing more likely to improve your gongfu than a haramaki. They help you establish a "frame" and relax the dantian. My advice, toss in the towel with all that core strengthening gobbly gook and just get yourself a haramaki!
I have one wool and two stretch cotton haramakis. This is the type I have, (Item No. mn-1002, mn-1003) scroll down...find the products second from the bottom!
You can read more about fashion and health benefits here, and here, and then there is Haramaki Love.
In China the generals used to wear a very heavy tiger skin attached where the haramaki is, it would hang down to their knees and probably felt something like an x-ray apron. A softer lighter version was worn by children and used by women for the month after pregnancy, when they were most vulnerable to spirit invasion. The tangki, or spirit mediums of Singapore and other places where Hokkien culture is strong, wear this kind of bib (tou-ioe) when they are possessed by war gods and when they are possessed by baby or child gods. The tiger skin is worn ritually in Tibet and of course Shiva wears one too.
For internal martial artists the image of the heavy tiger skin apron is a reminder to first let the muscle mass of the lower body hang heavily before the mind moves the qi (and the mass follows the qi, of course).