So what you need to do is break this into multiple paragraphs to drill down in the action:
"...easily accessible for the guards but hidden away and hard to get to for the threat, be it a bomb or a one-man army.”
Chester stopped talking and took something out of his pocket, it looked like a Digi-Map, but this one was empty.
(insert text here)
“Now the most likely place something like that would be placed would be either underground,” he marked the Digi-Map..."
Notice the bold text in the second paragraph. The narrative voice is going to be telling th audience what a Digi-Map is. We don't know... we don't have these... it's all in your creative head. Chester taking something out of his pocket is a complete sentance. After this, describe what the hardware looks like. What's a digi-map look like? Is it a pyramid that projects the hologram from the tip? Is it a small ball held in a hand that projects outward? What color is it? Does it have lights or buttons or lens and are they on or off? Imagine going to the year 2000 and describing just what an iPhone looks like. Becaues year 2000 me is going to look for a flip phone, with number pad keys, an attena, and a big letter I on it... 2000 me has no concept of a touch screen or a single button for the entire physical user interface. Hell, I have no idea what the significance of a full vs empty Digi-Map is... so you need to explain this to your readers (I have an idea from inference that it's a map that the user has to create rather than a map that someone would buy, say of the state or the world. Personally, I find the consumer packaging details to not be a great deal of importance to the scene and call this "Biblical Info"... that is, you the aurthor know this detail as part of your world building, but I the reader, don't need to know this fact about Digi-maps are sold with both pre-programed maps OR Tabula Rasas for user generated maps). Finally, how used is it? Is it fresh out of the box or does it show wear and tear.
Second bolded paragraph needs to describe the change of state when it's activated. Let the reader know it's a 3-D map projection... but again, paint a picture for us (what color is the hologram? Is it like watching a model with tiny moving figures or is it a 3-D blue print? Is it solid in appearence, or does it flicker like Star Wars holograms? When he touches the part of the map, how does the image change? Is the area a crudly drawn red line, or does it react some other way?).
Either way, when I read your book and then years later hear it's being made into the must see summer blockbuster/HBO series, your work should describe a Digi-map to such a degree, that the special effects are exactly the same thing I see in my minds eye when I imagine the scene.
In both cases, remember to show some reaction or recognition of your viewpoint character. If I met 2000 me and showed him my iPhone, he'd be blown away by all the amazing things I can do with a device that fits in my hand. (Hell, the fact that I have Pokemon GO! on my device alone would blow his mind. 2000 me would be in the middle of the original Pokemon craze... 2020 me would know of 8 generations of the game.). But for me, my iPhone is 6 years old and woefully outdated... they're releasing iPhone 13 at time of writing, meaning my iPhone is 7 generations behind. The 13s are more bleeding edge to me, then my iPhone6 is to 2000 me! Or to put this another way, showing the internet that I have an iPhone 6 is met with reactions of "Wow, what a geezer" where as showing an iPhone to a person in the year 2000 is tantamount to revealing that we also have flying Deloreans.
The dialog is broken off into seperate paragraphs because all action in a chapter/scene, including narrative exposition, is seperated by a paragraph. The narrative voice describing cool future tech to the reader is action. Chester speaking is action... they cannot occupy the same moment in time, so they cannot occupy the same paragraph.