I have only used "military grade" items for various applications. The AN PVS-14 is the most versatile item, as it is a monocular. It can be helmet/head harness mounted , and thus used to navigate and observe at night, but to use it head mounted and employ a weapon you need a laser on the gun. The 14 can also be mounted on a rifle like the AR15, stacked behind a sight like an ACOG or M68 aimpoint. To observe with this setup, you need to raise the weapon (and thus point it at everything you are looking at). You don't need a kevlar helmet- there are various harnesses or they can be mounted on PRO-TECH hockey type helmets (this was a common practice where I worked on recon operations). Another great piece of NV gear is the Universal Night Sight (UNS) AN PVS-22 (or 26, or 27). They are modules that mount on extended rails in front of a day sniper scope, making that scope a night scope. They work great, but they definitely make the rifle cumbersome and top-heavy (and sniper rifles are already pretty heavy) so you need a bipod, sandbag, window sill, or some other type of solid support. Except for crew served weapons like machine guns, we never weapon mounted thermal sights- but we did use mini thermals (about the size of a digital handy-cam) for observation. All of this stuff is pricey. I'm sure there are civilian versions of all of it, but when it comes to NV and thermal you definitely get what you pay for.
