What to use as a mirror for martial arts practice areas

I don't have the space to do it right now, but I think in the future I'd like to have an indoor practice area. One requirement for the area would be a mirror so I can observe my own movements.

My concern is that a traditional glass mirror would easily break and with weapons flying around it's pretty likely I'll hit it.

I've heard of acrylic mirrors, but they don't seem to really be break proof. I'd imagine eventually this mirror will be hit. I also heard something about stainless steel or other metal mirrors, but I actually haven't seen one of these. Any recommendations?