Movie has a great premise and an interesting setup similar to "Buried", "Locke" or "The Wall", where most of the action is just the lone protagonist communicating with disembodied voices on a radio or cellphone. The post-apocalypse narrative was what I came for, so I was disappointed that so much of the film's scant 83 minute runtime is given over to a distractingly creepy "Pretty Woman"-style romance subplot presented as flashbacks. And when I say it's creepy, I don't mean in the way you want your horror movies to be. I mean the way the controlling, wealthy romantic interest, having met the main character once, later follows her home and then later still imprisons her in his own home until she kicks her heroin habit and falls in love with him. Stockholm Syndrome? The movie acts like this is normal and sweet.
Back in the main storyline, the titular "Hostile" creature is well designed and well played with the correct kind of creepiness to his movements and appearances. The standoff between the creature and Juliette eventually reaches its necessary showdown, to good effect with some nice echoes to "Predator".