Nightsiters seem like a good gimmick to sell some extra UV flashlights. And why would I want to "quickly charge it if necessary?"
I can see the situation unfolding like this:
*CRASH* Your front door window breaks and a couple of burglars enter your house in the middle of the night.
You suddenly find it necessary to charge your nitesiters. "Hey burglars," you yell downstairs, "give me a few moments to charge my nitesiters night sights! I can't find the darn UV flashlight in the drawer. Ah there it is. Just give me a few seconds to charge them up. OH DARN IT! One of the industrial adhesive dots has fallen off...where did it go??"
"It's on your forehead," one of the burglars says right before shooting you. *BLAM*
Hey, it's your life...do you really want to be cheap?