I worked on a system similar to this for a man with an prosthetic arm. We stuck a temperature sensor in the finger of the prosthetic hand, and used a small thermoelectric plate which contacted his skin where the prosthetic attached to him. The back side of the peltier plate was glued to an aluminum bar acting as a thermal source/sink, and the front side had a small stainless plate acting as the contact point with a second temperature sensor bonded to it for feedback. Using a microcontroller and a bit of simple hardware, we made the peltier plate temperature equal to the temperature detected at the finger. With some limits, of course.
The man went from having a plastic arm to having something that *felt* like an actual part of his body again. He described going home and touching his wife's face, and almost breaking down crying - it felt pretty good to hear that, especially since it only took us a few days to design/build the thing.
Anyway, it ran off three NiCd AA batteries and had a battery life of about 24 hours - he'd plug it in to charge when he went to bed, and it would easily last until the next charge cycle. These days thermoelectric devices are more efficient, batteries are a lot better and microcontrollers have much better power consumption.
There's a few things that make a system like this fairly low power:
- You don't need a big contact area to get the sensation of temperature across to the user - you don't need to heat or cool their whole hand. Half a square centimeter is plenty if you put it at a fairly temperature-sensitive part of the hand, such as where your fingers meet your palm. It'll feel weird at first but the 'immersion' feeling will eventually set in.
- There's only a narrow range of temperature that you have to drive the contact plate to. You don't need to do 0 to 50 degrees C, and I fully expect Sony to restrict the range to +-10C at most for liability reasons, not to mention practical reasons.
- Skin isn't *that* thermally conductive.
So if your contact plate is sized small and only within a few degrees of body temperature, you're probably only moving half a watt at most between the hand from the contact plate.
Secondly, I seriously doubt the thermal "immersion" effect will be running all the time, probably only acting on 'events' the game - walking indoors/outdoors (pulse of hot/cold), picking up a weapon from the ground (cold), getting hit with a fireball (hot), falling into water (cold), etc. Much like vibration motors in controllers don't run all the time.
End result is that running the thermoelectrics won't take that much power, and sinking/sourcing heat from within the controller shouldn't be that hard. Overall, seems pretty practical to me.