I have heated grips on my ST4S.
They are after market jobs, and work a treat.
I have the temp control unit attached to the left hand side black plastic fairing trim. The cables from the grips reach over to this location without too much of a problem. It is held on with double sided tape.
Mine is wired directly to the battery, but this isn't ideal because if someone decided to turn the grips on while the bike is unattended it could flatten the battery. My mate with a 4S has his wired to a fuse in the fuse box (not sure which one, but it is the one that has its power cut when the ignition is off). For this reason I unplug them when not in use
Fitting the grips can be a bit of a mare as they aren't very squashy. The big problem for me was getting the throttle grip on. The original grip is very thin rubber, and the inner plastic shell has lumps on it to stop the rubber from turning on it. You have to doctor this a bit else the heated grip squashes it in so it doesn't spin freely on the handlebar. I trimmed it a bit, but not enough, so had to sand the inside a bit to give enough clearance. Once the grip is on it aint coming off again !
The left one is held in place with hair spray (helps it slip on, then sticks it in place
).
The ones I brought had the grip ends covered over for some reason (I probably picked up the wrong set !), so I had to cut the end plug off. It doesn't notice in the slightest as the cut is covered up by the bar ends.
I think I got them from MPS or M&P, and they cost about 45 quid.
I'm now working on heated grips for the pillion
I hope that is of some help.
Cheers,
John