Therefore the shirt mod was born.
This makes the pocket always buttoned, accessible and will prevent the corners from rolling up over time.
This is by no means original, Police uniforms have this often done to them, that's where I got the idea.
Step 1: What You Need:
A shirt. (You already have it, otherwise you wouldn't be needing to do this.)
Thread, of color to match your shirt.
Sharp thing (knife or scissors)
You may want:
Sewing Machine (Any regular machine works well.)
I do my work with a machine, I am lazy. This is a very simple job, a complete novice should be able to use a machine on this, and if you can avoid blood stains, hand needle will work just as well.
Step 2: Remove Old Buttons
I find it best for the shirt to use a pair of sharp scissors, open them up, and place one blade behind the button to be removed. Place the sharpest edge (inside) against the button and slowly work it through the threads maintaining a slight tension between the button and the fabric. This prevents the sharp from cutting into the fabric. I don't suggest simply snipping the buttons off, you may lose them or cut into the shirt.
Clear away the threads from the shirt at this time.
Step 3: Sew Buttons Onto Flap
If you are using a machine, set your stitch length to 0 and your width to 3mm (This is a standard width.) For the first pair of holes, hand feed the first two stitches to make sure they are lined up. (I broke a needle very quickly by being just a little off.) Propping up the back of the pressure foot will make lining up the button much easier.
Trim away your threads before the next step.
Step 4: Sew the Flap Edges Down
If you keep your stitching along the lines of the original stitching, it will be practicably invisible.
Make sure that you don't have any extra shirt behind your stitching.
Be certain to line the pocket up so that the flap will lay flat when you are done.
Trim away the spare thread.
Step 5: Wear, Use and Enjoy!
The pocket contents can still be accessed by lifting up on the center of the pocket flap (where the button is) but will instantly be closed upon release.
This has the added benefit of being more secure than the original pocket, your phone/notepad/I-Pod cannot easily fall out.