I've watched this guy's progress on developing a NV rifle scope. It's essentially just an IR camera coupled with IR illumination. https://www.youtub...atch?v=FLpqHv1fmQU
Check out some of his other vids too.
IR illumination does have some weaknesses for shooting applications, but for UE, I think it's a cheap, easy, and effective route. Just be careful with certain IR illuminators, IR lasers can cause permanent eye damage if directed at someone.