I seriously doubt that this is the case. The current (amps) required
to provide the power (watts) that these kind of devices typically have
is beyond the practical output of a 12 volt electrical system. This
would be even more so the case in a device that needs to be on for more
than a few minutes. The hair dryer may be the exception but the heat
output would be much less than even a travel type 110 volt a/c model and
would provide most of its drying capability with it's airflow. 12 volt
coffee makers are available and take much longer to brew but the one I
had worked fine until it died. Portable 12 volt heaters, no way. Even
with the engine running, a 1500 watt heater would kill the battery in a
couple of hours. Also, it would have to be wired directly to the battery
with at least 6 gauge wire.

Mark Drillock