I would have a loud-speaker. The unearthly voice booming out would terrify them. I could scream that I was a god and that if they didn't step back my wrath would be upon them.
The other item would be a very, very bright torch - that should scare em stiff. Booming voice + Flashy light orb = scared superstitious primitive. Oh come on, they WERE primitive by today's standards. EVERYONE was a primitive back then, and they all believed in nonsense like Magic and Super-natural powers. My plan to scare em with new technology would work. Not for very long, but long enough for me to get the hell away.