Just found a really good t-shirt for insulin pump users. I don't have an affliates deal (but ought to look into it). They are currently on sale. Black only.
I have one on now, and the earbud holes work perfect for passing through tubing -- my inset connector passes through fine.
They are on overstock sale at Think Geek right now.
ScotteVest has it in other colors and other fabrics. I'm real happy with mine and ordered more.
Quoted from http://www.thinkgeek.com/tshirts-apparel/unisex/generic/af26/:
So when ScotteVest came out with their 100% cotton version of the same shirt, we jumped on it.