Spark Fun has general purpose light senors and color light sensor but you do not have sensor specifically built for ultra violet light.
I’m thinking of an inexpensive UV A & B dosimeter. A UV A & B light senor connected to a micro controller and logging to a SD chip. That way you know how much you are exposing your self to sun light and you could even test sunscreen with it.
If you want to start out simple you could implement the circuit shown in the website below.
http://www.scitec.uk.com/uvphotodiodes/ … easurement
It would require an opamp, resistor and capacitor to convert the current from the UV senor to voltage.
I have been thinking of adding this senor to the package tracker board myself.