A thermometer in a Steam Room would be ideal. However, we have yet to locate one that holds up to the heat & humidity of the steam room environment.
Also, the commercial steam rooms can have a very dense fog making it near impossible to read the interior thermometer.
The solution I can offer is a thermometer that mounts outside the room informing bathers of what the temperature is prior to entering.
Check out the PreciseTemp320 Digital Steam/Sauna Room Thermometer at www.steamsaunabath.com