http://www.overclockers.com/lamptron-fc10-fan-controller-reviewGives you the option of displaying Celsius temperature via probes, fan RPM or voltage. This controller could also potentially be used for things other than computer case fans.
The review concludes by stating "An MSRP of $69.99 may seem steep for a fan controller, but considering
the power of the channels and work involved to make the unique display,
the MSRP seems fair to me. Lamptron also mentioned that they have been
having issues with fulfilling production of the FC10 due to a lack in
supply of Nixie tubes themselves. Therefore, there is very limited
quantity available worldwide of this product. Overall, as long as the
Nixie tubes are working, the FC10 is a great controller for people who
love the old industrial theme and need to control many fans whether low
or high wattage."
I can't tell what tubes they're using, though they look a bit like B5092's.