Has anyone installed any heated grips on their hammer? If so what kind. I was looking at heat demons so i could keep my custom grips.

You're on the right track with that Heat Demon kit. You may be able to find a better price on a similar kit, but the less expensive models usually only have "Off/On" or "Off/Low/High" settings, it looks like the Heat Demon kit has 4 levels, which would be pretty handy. It seems like whenever I ride snowmobiles in warm weather (warm being a relative term here) I'm always switching the grip heaters on and off because they get blazing hot and my hands start sweating.

I'm looking at the Heat Demons as well for my bike. Did you or anybody else ever purchase these?

I had heat daemons on my last bike and can't say enough good things about them. Easy to install. Mater of fact one side quiet working so I went to there web site emailed them and the next day had my answer. Two days later the part was at my door free of charge. Look at there web site you have questions write them. I'm not sure but I think you can buy from them if not tell them wear you are. Any after market bike shop can order them for you and maybe even your dealer.
Rode with summer gloves late into the fall cause of the Daemons