It's been a while since I added anything useful to the forums, so here goes:
I rode all last winter without hot grips and I'm f**cked if I'm doing that again this winter.
Grips can simply be wired directly to your battery, but if you forget to turn them off when you leave your bike you might end up needing a bump start.
I've also heard of wiring them directly off the bike's loom, but I don't like the idea od putting extra load on the loom with non standard parts. Grips can draw a fair bit of current and if it screws up the loom you're in for a world of pain.
I'm not going to bother with the actual grip install, this is pretty straight forward. I would recommend running all wiring on the opposite side to your throttle cables though and use plenty of zip ties and anchors to keep the wires out of harm's way. I didn't solder anything but used proper male/female connectors similar to the ones used by Kawasaki for the rest of the electrics.
The part that's tricky to find information about is the wiring of the relay. So, here's a nice simple diagram I made to explain the way I wired things up:
I used the +ve wire from one of my tail lights for the relay trigger - that way the grips will only work when my tail lights are on. One the bike is switched off the lights being off will cause the grips to also switch off automatically.
This means the grips wont work unless I ride with the lights on, but I usually have them on anyhow so it's no biggie.
It's a 2 pole relay - tab 87a on the relay is powered when the lights are off, so I can wire in a flashing LED to make it look like my alarm actually works if I wish.