What are these creeping cacti tendrils?
It's creepy ... something I find fascinating. 


Creepy &amp; fascinating indeed! 


  Could someone tell me what this cactus-y, bed of vines-like plant is?


This is a cactus, and I believe it belongs to the genus Hylocereus, possibly the species H. undatus.



As for distribution, Hylocereus are quite prevalent throughout Hawaii, and can also be found scattered throughout the globe. 


Hawaii is the leftmost blue dot. image source

More information about this plant can be found here.