But for any device that producesrequires heat (toaster, portable heater, hair dryer, clothes dryer, towel warmer, dishwasher dry cycle, etc.), the efficiency of mining is infinitemitigated.
The efficiency isn't going to be perfect because the nature of the heat may not be fully fungible with the original source of the heat in such devices.
It certainly will for some of these devices. A portable room heater being one example. That is absolutely 100% efficiency. There is nowhere else for the heat to go. In most of the others the device can be designed in such a way that the efficiency approaches or reaches 100%. For example, in the case of a hair dryer you can put the mining chip at the air intake before the coils and reduce the power to the coils by the same amount. You get the same output as before. Clothes dryer, etc. is quite similar.
On the mobile/IoT side I think they are looking more at the distribution aspect and less at the efficiency of mining being significant.
EDIT: okay sure, there are RF emissions, and the deliberate power output for WiFi or mobile, but that is negligible compared to even 10 W of actual mining power. There is still no question this far exceeds the efficiency of dedicated mining.