[@Savo]
The firearm is mainly there because it is something he cares about, he doesn't plan on actually using it. I said strength-based power as an example, telekinesis that is stronger than peak human (Or pretty much anything that is stronger than peak human strength) could keep something from being consumed. Tendrils move relatively quickly, about the same speed the average man could run (Let's say 10-15 miles per hour). Tendrils are made of a flesh-like material, slimy to the touch, and have an extremely strong grip strength. They can be cut with something sharp like a knife about as easy as it would be to cut someone's finger or foot off. Blunt damage doesn't do much, though, unless it is strong enough to be superhuman.

So you could stop something from being assimilated if you knew it was coming, and the tentacles don't hurt people or living things - just tries to drag objects to the phone. So, you could fight it off if you had a sharp object or a power that was strong enough to crush them.