Portable Mini Motion Detector Alarm + 120DB Ear-Piercing Siren + SOS LED Light, Hotel Door Room Security Device for Female Women Kids Life Safety While Travelling Alone 2-Pack

If you're in a more remote area, you can buy cheap motion sensors that go off if someone gets too close. Obviously, not as good as a lock or a secure site, and isn't an option at sites with lots of movement, but it can be helpful when you're in remote areas and feel a bit exposed. https://www.amazon.com/dp/B087JKVF3Y?ref=ppx_yo2ov_dt_b_fed_asin_title