In SA OC Siman 301 it's discussed many of the things a person can and can't go out with on Shabbos in a place where there is no eiruv.
Is one allowed to wear a armband or wristband on Shabbos with some sort of the reflective material on it in a place where there is no Eiruv? This way at night cars will better be able to see the Orthodox Jews crossing the streets. As well this is only worn at night and not during the day at all (it's taken off when one arrives in shul obviously and a person probably wouldn't want to wear it at all during the day.) What is this similar to if anything in regards to what it says in SA OC Siman 301? What other comparisons or examples or proofs to this could be give?