I've often used touching glass windows as a quick way to check temperature. This device is intended to simulate that. A combination of a heater (easy) and refrigerator (harder, but doable), would cause a panel on the device to feel the same temperature. The device itself would set its own temperature based on a wireless technology, either from a thermometer placed outside or from a a weather report.
Technology note: In general, this relies on three pieces of technology: 1) A heater (e.g., a metal coil). This is trivial 2) An air conditioner/refrigerator (doable in a portable form factor 3) The inside of the device will probably have a block of material with medium heat capacity, high thermal conductivity, low volume, and high surface area (low volume and high surface area basically just means a lot of grooves), with part of thermal material exposed on the outside of the device.
Note: The thermometer doesn't actually have to a true match for the actual temperature; materials with higher thermal conductivity feel warmer/cooler.
This is kind of a weak product, but it's a much more intuitive way to answer the question, "what temperature is it outside?" than a thermometer. I could imagine using this as a physical aid when informing children, "it's cold outside" or "it's hot outside".-- aguydude, Nov 29 2017 Degrees Subjectigrade Degrees_20SubjectigradeA complementary idea [pertinax, Nov 30 2017] [+] but the title's a bit scary.-- FlyingToaster, Nov 30 2017 Forget the air conditioner / heater combo and just use a simple Peltier.-- RayfordSteele, Nov 30 2017 Good call, RayfordSteele. That makes this invention way simpler.-- aguydude, Nov 30 2017 random, halfbakery