LED temp faucet

I saw this really awsome faucet. It turns on a blue light when the temp of the water is cool. And a red light when the temp of the water is hot. I was thinking we could do something very similar, with some simple electronics. Any one have some good pointers for doing this? I would like to cool version, but can't aford it just yet. How about some ideas?

So has no one got anything else new?

I saw this one.
http://www.ministryoftech.com/2006/08/29/faucet-changes-color-with-temperature/

You could start off with a thermistor (temperature-dependent-resistor) but I'm not sure if this would react fast enough though. Here are two suggestions, I don't if they are feasible since I do not know anything about the available values of thermistor or their characteristics regarding dependence on temperature.

1) Simple method:

from wikipedia http://en.wikipedia.org/wiki/Thermistor
PTC has increasing resistance with increasing temperature, connect this in series with blue led.
NTC has decreasing resistance with increasing temperature, connect this in series with red led.
Calibration would be quite a time consuming process and it might be tricky to find the correct values and types of thermistor.

2) Better method

A better method would be to use the thermistors as a potentiometer in a driver circuit e.g. the 'shark' from the Sandwich Shoppe or 'Fatman' from Taskled. Again this would require very specific values of thermistor. Calibration could be performed using a variable resistor in series or parallel with the thermistor.

This might work. They also make some pretty easy kits that I could use a micro controller for $50. Then the lights would only require software programming reading the thermister and when the thermister reaches threashold temperatures, you turn on the apropriate LED. This could be software compatible with anything.

The nice thing about the built in solutions, is they are made to have electronic temperature control at the faucet. You set the temperature and you get electronic mixing of the water till you get that temperature.

This means when you turn it ON and the water is too cold, it turns on just the hot until the temperature gets to the temperature you want, and then mixes in cold water to keep the water the temperature the right temperature, using what is called an electronic mixing valve.