A current-sensor would be useful in a lab power supply. This app note is about chaining two current-sense chips to use at high voltages:
Using a transistor as shown, you can double the allowed voltage limit on a current-sense amplifier by stacking two such amplifiers one upon the other. The voltage signal from the bottom amplifier then represents current as the voltage across the sense resistor, times the product of the gains of the two amplifiers.
Thanks for the tip rsdio!