Here's an idea - morphing fabric

This probably exists already.

What about a fabric that has the ability to be porous / breathable like thin lycra, and then at the touch of a button it turns wind-proof?

Open knit, with big spaces for air to flow -> push button -> tight knit, no airflow.

Think of the uses, particularly in sport. Cyclists or runners. If the air is cold at the start of the race, keep warm with the 'no airflow' option, but as soon as the blood is pumping, keep as cool as if wearing the thinnest vest. If there was a way to regulate in in an analog way, even better.

Of course I have no idea what specfic technology could/would be used. I haven't even googled the concept.

Whether it would move a blocker into the holes (like a shutter), or whether the fabrics just thicken (something like, but completely different from muscle wire) is up to the scientists.

Here's another application where it would be really useful: Don't you just hate it, in winter, when you walk into a pub and you have to take your coat off (and keep an eye on it all night). Well if you were wearing one made of 'magic material' just open it up and be cool.