I put pens in my pockets. However, sometimes I put them in without caps, or I put in retractable pens without retracting them to keep the tip inside.

The result, as all who do this know, is from time to time a pen leaks out and ruins a pair of pants, sometimes more than that. It's expensive, and hard to solve. Since the earliest days the badge of the nerd has been the shirt pocket protector, but I put them in my pants. You could try tyvek pocket liners, I suppose, but it's hard to see how to easily add them.

I wonder if we couldn't come up with designs for retractable pens where there is some timed decay to the extension of the tip, so that it automatically returns to being inside after a modest time, perhaps half an hour to an hour. It could either just return at a very slow pace with the spring pushing back against something firm enough to keep the tip in place, or something that slowly bends and releases the ratchet. The latter is better because of course the tip must be firmly held for writing, we don't want to be able to push it back in with the pressure of writing.

The time to return might well be fairly short. Today I find that I only use pens for short bursts of writing. I do all serious writing on a keyboard. I will pull a pen out to make quick notes and then I am done. While it might be annoying from time to time, I could even imagine it clicking back after just a couple of minutes. Of course many pens would not do this -- which is a problem, because one will still be regularly picking up other pens, as one often does. But you could still reduce the number of times pen accidents happen if you bought mostly pens like this for yourself.

Electronics getting as cheap as they are these days, this could also be done instead with a sensor. Clicking the pen to extend the tip stores energy in the spring and might store it elsewhere, so that after a couple of minutes it beeps if it hasn't been reset.