Constructing a simple emergency light kit
Looks pretty good, but keep in mind the transformer is an AC signal, and will oscillate between +9V and -9V.  Therefore, it could be "on" but still result in base current during the low parts.  

The way stuff like this is often done is to take the absolute value of the output of the 9V transformer, using a circuit configuration known as a full wave rectifier, and then you would use a resistor and a capacitor configured as a low pass filter to smooth out the remaining waveform to near its rms value.

This picture from http://en.wikipedia.org/wiki/Rectifier shows the config and the result