grip surface for exterior stairs

[sluggo]

Hi, What are some good materials to place on the tread for my exterior stairs? I've thought of thin wire (may cause a toe to catch on it though) and roof shingles (which easily shed/wear), but I think there must be some better materials. thanks

[ShadowTek]

Maybe that chunky truck-bed stuff would work just as well?

You can find truck-bed liner by the quart at Walmart, but I can't remember if they also have the chunky stuff.