I used some tie-downs when I moved the bike a while ago, they cut into the grips but revealed the heating element underneath. It's a printed circuit on a thin film polyester ... I've seen the 'old' types which use constantium (?) wire as the element and once those are shot they're ...um shot, but I think you'll be able to peel the 800's grips off and re-install new ones as normal.
That link that Gunz gave you ... those grips are great, but I wouldn't arse around like that, and personally I hate fat grips... I'd just fit them normally.
Greg