I had a few places locally quote me for it.. couple of them emailed back almost instant quotes way too cheap indicating that they had no idea what might be involved... the only one I actually might have trusted to do the work indicated I'd be spending something of the order of $500 and have to sacrifice an activated key - but on reflection decided I could buy a nice warm jacket and driving gloves for a whole lot less
The Volvo remote start accessory is not available for the C70, at least the last time I checked some years ago. There are several aftermarket solutions that I looked into but all involved carrying around another (ugly) key fob. If you're looking for a winter solution I recommend having the seat heaters turned up (at a dealer or getting a VIDA setup). For me, that usually takes the edge off real quick, so much so that I pretty soon turn the seat heat down to the lowest setting.