There are many products out these days to solve your problem. Epoxies,urethane's, and sealers (tinted or clear) can all have sand,glass beads, or rubber added to them for a non-skid surface. Any good paint store or hardware store can supply these and give ideas! But the prep work before you try any of these is critical. If the concrete is fairly new and not stained, a good wash and pressure wash rinse might work. If it's older but only lightly stained, acid washing will work(wear ALL the protective gear). If it's highly stained(lots of old oil,etc) then bead blasting is recommended.