There's one "built in" to the JR Ballistic gloves I have. I think the glove itself does actually work better if you're wearing textiles. However, leather gloves don't wipe off rain very well, and one of the wipers would come in handy...
my leather one does, must be just me though :cheers:
The fact that whether you use you glove or this wiper, you're gonna have to bring your hand back up again and again, I agree with the above post, keeping your visor clean is the best thing you can do, that way the wind takes most of it away.
I wipe my visor off and clean it at work most days.