My Joyetech VT full kit arrives tomorrow, and it's high on my list for validation

I haven't yet probed any coil heads, so it'll be interesting to see how possible that is - I'm pretty sure I can manage something though. What I expect to find is that the 450 - 500°F they quote is more like 400-450°F at most; that seems to be the case with the Ni200 heads from Kanger and others. Always requires a setting higher than is actually achieved - no doubt due at least in part to the longer wires required for coil heads versus self-built coils in RTAs and RDAs.
Your wish will soon be answered in the form of the new Innokin thermometer-in-a-tank system

It will require their mod and their special tank, but it will temperature monitor any kind of coil, including Kanthal. In theory at least, and it's looking promising from the videos they've done.
Of course that does seem to be limited only to their coil heads, to start at least. No word on when, or even whether, they will make one that allows rebuiladable coils - an RTA with a sensor, basically. My guess is it will come, but likely not in the first release.